Etymology/history of "dib-dob" as military slang for foreign currency

AFAIK
dob (ODO)

verb [with object]
NZ, Australian
informal
2 (dob something in) Contribute money to a common cause.
‘everyone dobbed in a few dollars’
Origin
1950s: figurative use of dialect dob ‘put down abruptly’, later ‘throw something at a target’.

EDIT
HMS Ark Royal's Royal Naval Slang & Terminology
Mentions only Ickies & Klebbies for Foreign money.

Ditto, Jackspeak: A guide to British Naval slang & usage (GoogleBooks)

Commentary:
I can only extrapolate that dib-dob is no more than fanciful reduplication of dob.

See also:
What is the origin of “dibs”? (ELU)

Well, I can't find anything else online about anyone actually using “dib-dob,” but as far as its presumptive etymology:

Every applicable sense^_¹ of “dib” or “dob” in the OED traces its origin back to dialectical variants of “dab,” usually with the intention of making the referenced pat of something somewhat smaller. The game dibstones, played with sheep knuckles as a kind of jacks, led both to Americans “calling dibs” and to dibs meaning

3. plural. A slang term for money.

1812 H. Smith & J. Smith Rejected Addr. 111

Make nunky surrender his dibs.

So ultimately on both sides it refers to small dabs or pats of something. The word “dab” itself shows up in Middle English with no apparent predecessor and seems to come from onomatopoeic imitation of the sound (now *splat*) of a small dab of something being flicked down.

^{_{¹ “dib, v.¹,” is a variant of “dip” in reference to any small lowering. “dib, n.¹,” is a variant of “dip” in reference to a piece of land that dips down. “ dib, n.³,” is a variant of “dub” in reference to puddles of water.}}