Is the idiom "as neat as a pin" an American phrase?

I'm editing a novel set in 1930s England, written by an American author, and have been editing out any Americanisms I come across. I just read a line of dialogue containing the idiom "as neat as a pin" (meaning clean and tidy). I've never heard of this before; is it an American phrase, or have any other Brits out there heard of it? All I can find of it online is that it originated in the early 19th C. with the development of mass production.

If it is in fact an American phrase, what would be an appropriate British English equivalent in keeping with the book's setting? "As nice as ninepence" perhaps?

The Oxford English Dictionary's earliest reference to the phrase is 1787:

e. as neat as a (new) pin.
1787 Columbian Mag. I. 636 [He was] neat as a new pin. 1801 J. Wolcot Wks. (1812) V. 35 How neat was Ellen in her dress! As neat as a new pin! 1849 Thackeray Pendennis I. xiii. 118 Major Pendennis, whom Miss Costigan declared to be a proper gentleman entirely,..and as neat as a pin. 1933 L. A. G. Strong Sea Wall 245 Sheehan's pride was to have his cottage as neat as a new pin. 1961 Dog World Apr. 30 In the morning we leave the room looking as neat as a pin!

Although the first cited reference is a Philadelphia journal, the second cited reference is from the British author John Wolcot in 1801. I think we can assume from this, and many other British sources from the 1840's onwards, that the term has long usage in both American English and British English. Consequently it would be appropriate to 'put it in the mouth' of a speaker of British English in the 1930's.

Earliest confirmed occurrences of 'as neat as a [new] pin'

Although (as noted in John Mack's answer) the OED identifies a 1787 instance from the Columbian Magazine—a U.S. publication—as the first occurrence in print of the phrase, "neat as a new pin, searches of the Google Books and Hathi Trust databases yield instances from 1765 and 1771—one from a London magazine and one from a book published in Dublin. These findings seriously undermine the hypothesis that "neat as a [new] pin" originated in North America rather than in Great Britain. Following are the two earliest instances I am aware of.

From "Vastly Short, but Vastly Clever Notions of Matrimony," in The Jester's Magazine: or The Monthly Merry-Maker (November 1765):

To be sure Mr. Sprightly is a vastly polite Man, and I am sure I am vastly fond of his Company.——Well! I hope I shall have him, for he saluted me with a vastly pretty Compliment this Morning. "Miss," says he, "you are as neat as a new Pin." Oh! Gemini! thought I, that was vastly endearing.

The Jester was published in London.

From Thomas Bridges, The Adventures of a Bank-Note, volume 1 (Dublin, 1771):

The honest man [a stock-broker] having confessed he had cleared above two thousand pounds by the lye of the day, she wheedled him out of a note for a hundred for her own use; and he could not have bestowed it better, for she is a comely agreeable dame, and always as neat as a new pin.

Although this novel was published in Dublin, his Wikipedia article identifies Bridges an an Englishman, born in Hull.

Other fairly early occurrences of 'as neat as a [new] pin'

Several other instances from the period 1790–1810 appear in Google and Hathi search results as well, all of them published in the British Isles.

From an untitled poem in The Nose (London, January 1800):

By some philosophers, 'tis said, / A widow's neither wife nor maid / And some I know will take their oath, / A widow's better than them both. / Now with a widow we'll begin, / As neat and polished as a pin; / And what was more, in prime of life, / Six years a kind indulgent wife; / And what was more, a jointure large; / And what was more, without a charge; / And what was more, in ready cash; / And what was more—we'll leave a dash!—

From Peter Pindar, "Orson and Ellen: A Legendary Tale," in Tears and Smiles: A Miscellaneous Collection of Poems (1801):

How neat was ELLEN in her dress! / As neat as a new pin! / By this she brought full many a pound / To BONIFACE's inn.

From Peter Pindar (again), "Elegy to the Same [that is, to the King]" in Tristia; Or, The Sorrows of Peter (1806):

Then there's Sir FRANCIS! how polite a man, / So worthy, and his character so fair is, / Pays all his debts! uncommon!—a black swan!— / Oons! down with Cold Bath Fields, and down with ARIS.

So handsome , and so neat as a new pin! / So like a gentleman in every feature! / Lord! what a shame Mainwaring should come in, / A shabby, nasty, black and ugly creature!

From Catherine Cuthbertson, Forest of Montalbano: A Novel, volume 2 (1810):

"It was in a pure dirty litter with dust and rubbish, that's a sure thing; but I wou'd n't be minding that same, so to work myself went, immediately, the next morning, and, like a sturdy Irish Hercules, I soon made light my Augean labour, and cleaned the platform out, as neat as a new pin ; and finding an elegant spring-board, out of practice, about the premises below, myself slipped up with it, and erected it there ; ...

Possible antecedents and variants to 'as neat as a [new] pin'

In addition to more or less precise matches for "as neat as a [new] pin," searches turn up several other "as a [new] pin" similes—some from before the earliest occurrences of the phrase in question and others from the roughly the same early period. Here are some of those instances.

From a translation of "Mr. John Nieuhoff's Remarkable Voyages and Travels into Brazil, and the Best Parts of the East-Indies," in A Collection of Voyages and Travels, volume 2 (1704).

The Fish called the Elephants Nose is of an odd Shape, its undermost Jaw being as sharp as a Pin. The Body is prettily spotted, with a broad Streak running cross the Middle. It is a very thick Fish, which is taken in the Sea, and in bigness and taste is not unlike our large Smelts.

From Jonathan Swift & Alexander Pope, "Sandys's Ghost: or A Proper New Ballad in the New Ovid's Metamorphosis," in Miscellanies, the last volume (1727/1733):

Now, as he ["a wit and courtly squire"] scratch'd to fetch up Thought, / Forth popp'd the Sprite [Sandys's Ghost] so thin, / And from the Key-Hole bolted out / All upright as a Pin.

From Jonathan Swift, A Complete Collection of Genteel and Ingenious Conversation, According to the Most Polite Mode and Method Now Used at Court and in the Best Companies of England (1737/1768):

Col. Atwit. Why, my lord, egad I am like a rabbit, fat and lean in four and twenty hours.

Lady Smart. I assure you, the colonel walks as straight as a pin.

Miss Notable. Yes ; he's a handsome-body'd man in the face.

From Issue No. 78 of The Batchelor: Or Speculations of Jeoffry Wagstaffe, Esq., volume 2 (May 2, 1767):

Jenny is every day as fine as a new pin, and as brisk as a bee. She frisks about like the flying horse on Temple-bar ; and is as full of tricks as an Antrim goat. I suspect the paints like a Bartlemy babby ; for tho' she is no chicken, she looks as fresh as a rose ; and I believe if she lives to be as old as Old Scratch, she will still be as merry as the maids.

From Peter Pindar (yet again), "Birth-Day Ode," in Instructions to a Celebrated Laureate; alias The Progress of Curiosity (1787):

Memorandum. ... Now having pencill'd his remarks so shrew'd--- / Sharp as the point indeed of a new pin, / His MAJESTY his watch most sagely view'd, / And then put up his asses skin. / To Whitbread now deign'd MAJESTY to say, / "Whitbread, are all your horses fond of hay?"

From "An English-Woman", The Adulteress ; or, Anecdotes of Two Noble Families, volume 4 (1804):

Madeline was so busy about her mistress—"this was so beautiful!—that was so handsome!—and as to yourself, Miss Emily," said she, (when she had put the finishing stroke to her dress, and was giving into her hand her gloves)—"as to yourself, though I say it, that should not say it, you are as nice as a new pin; and look so pretty in your wedding gown, that in my mind, you would make a proper wife for the Prince of Wales himself."

From Incidents, Marriages, and Deaths in and Near London, in The Annual Register, or, A View of the History, Politics, and Literature, for the Year 1809 (June 1, 1809):

The remaining fragments [found in the patient's stomach] are portions of the springs and linings of the knife-handles, some of them tapering to a point, and as sharp as a pin.

How American is 'as neat as a [new] pin'?

If we accept that "as neat as a [new] pin" probably originated in Great Britain, we might wonder what its status is in the United States today and how widespread its use was in that country in the past.

Bartlett Whiting, Early American Proverbs and Proverbial Phrases (1977) has the following entry for "as neat as a new pin" (all of the cited occurrences are to U.S. publications):

As neat as a new Pin

1787 Columbian Magazine 1.636: [He was] neat as a new pin. 1814 [William] Wirt, [The Old] Bachelor 159: She has me as clean and neat as a new pin. 1824 Tyler, [The] Verse of Royall Tyler 208. ...

The instance in the 1787 issue of Columbian Magazine appears in a letter from "P.Q." to the editor of the magazine, under the title "The Picture of a Beau's Dressing Room":

I had only time to notice, among other things, several sweet scented perfumes, a box of Keyser's pills and sundry pharmacopoeia, when hearing his [the beau's] foot on the stairs, I was obliged to desist from further observations. He came in, "neat as a new pin," and "blythe as flowers in May," and without any embarrassment invited me to be seated, and spreading his pocket handkerchief in one of his chairs, and taking the skirts of his coat in his lap, he set me the example.

The author refers earlier in this letter to "a night-cap [set on a bedpost], which from its colour and consistence, had not probably visited the laundress since the present revolution [a decade prior]," which suggests that he is an American writing from somewhere in the United States; but whether he was native-born or an immigrant from England and—if the latter—how recently he had arrived are impossible to say.

Whiting's book also has an entry for "as bright as a new pin" with an instance from a U.S. publications published in 1794.

Archer Taylor & Barrett Whiting, A Dictionary of American Proverbs and Proverbial Phrases 1820–1880 (1967), which covers the period immediately following the one that Early American Proverbs and Proverbial Phrases focuses on, reports multiple U.S. instances under the following headings: "dressed up as neat as a new pin" (from 1844, 1854, 1860, and 1869); "as neat as a pin" (from 1840, 1859, and 1860); "all fixed as nice as a new pin" (from 1833); "as slick as a new pin" (from 1844); "as straight as a pin" (from 1860); and "as sweet and clean as new pins" (from 1860).

Bartlett Whiting, Modern Proverbs and Proverbial Sayings (1989), which reports results—primarily from U.S. sources—for the period from 1900 forward, includes entries for the following phrases (with the earliest U.S. occurrence in each case noted in parentheses): "as bright as a new pin" (1935); "as clean as a [new] pin" (1932); "as neat as a [new] pin" (1930); "as sharp as a pin" (1959); "as slick as a [new] pin" (1930); "as smart as pins" (1934); "as spruce as a new pin" (1928); as straight as a pin (1941); "as tidy as a [new] pin" (1959); and "as trim as a pin" (1934).

Collectively, these results indicate a long (albeit varied) pedigree for "as neat as a pin" in U.S. English. The phrase seems natural to me despite my having lived in North America my entire life—but perhaps this comes of reading Peter Pindar from an early age.

To my surprise, none of the three books of American idioms that I have on hand—Christine Ammer, The American Heritage Dictionary of Idioms, second edition (2013), Cambridge Dictionary of American Idioms (2003), and Adam Makkai, ed., A Dictionary of American Idioms, revised edition (1975)—include an entry for "neat as a pin," although there is a brief entry for the phrase in Christine Ammer, The Dictionary of Clichés, second edition (2006):

neat as a pin Trim, orderly. This term dates from the late eighteenth century and appeared in print in several works by John Wolcot (who used the pseudonym Peter Pindar), as "neat as a new pin."

In contrast, three books of British idioms from my shelves include versions of the expression: Cambridge International Dictionary of Idioms (1998) has an entry for "be as clean as a new pin"; Longman Dictionary of English Idioms (1979) has an entry for "(as) neat as a (new) pin" (which the dictionary characterizes as "slightly old-fash"), and Oxford Dictionary of English Idioms, third edition (2009) has an entry for "clean (or neat) as a new pin."

Conclusions

The available evidence strongly suggests that "as neat as a [new] pin" originated in Great Britain, no later than 1765, although it also began appearing (albeit somewhat sporadically) in U.S. publications from a fairly early date (1787). I see no reason to suppose that the expression was ever more common in the United States than it was in Britain.

For a novel set in England in the 1930s, "neat as a pin" would not be at all foreign or anachronistic, although it might be even more authentic with "new" included ("as neat as a new pin") or perhaps with "new" added and with "clean" in place of "neat" ("as clean as a new pin").