Is "Canned meats, rated." a valid and correct English sentence?

Paraphrasing a bit what the others have said in the comments, these are not what we would call complete English sentences. But they are arguably full sentences, and there are circumstances when native speakers would accept them as such, e.g. in certain types of speech and prose.

Discussion

Note that while the definition of a (finite) clause is quite clear in English grammar, things are far murkier as far as the definition of a sentence. A finite clause—a unit consisting of a subject plus a finite verb and any complements and modifiers— is definitely a sentence, provided it begins with a capital letter and ends with a termination mark (i.e. a period, a question mark, or an exclamation mark). But must a sentence be a finite clause (or a coordination of finite clauses)? Arguably not. Consider the beginning of Dickens's Bleak House:

London. Michaelmas term lately over, and the Lord Chancellor sitting in Lincoln’s Inn Hall. Implacable November weather.

Arguably, Dickens meant these to be three sentences. But there is not a single finite clause among them.

Wikipedia has a serviceable definition of a sentence (here): a set of words that in principle, at least in its context, tells a complete thought; it may be a simple phrase, but it conveys enough meaning to imply a clause. And as far as functional grammar, all that's required of a finite sequence of words to constitute a sentence is, roughly, that it begins with a capital letter and end with a period, a question mark, or an exclamation mark (source).

When I say that your examples are full sentences, I mean that we haven't omitted anything. They really begin with a capitalized word and end with a period. In particular, I mean that they have not been extracted from larger sentences (though clearly there are some larger sentences to which they are intimately related, e.g. Pencils have been handled).

On the other hand, your examples are not complete sentences. My impression is that when we qualify sentence by complete, we really do mean that the sentence is either a finite clause or a coordination of finite clauses. For example, in the article It's totally okay to write incomplete sentences, the adjective incomplete clearly refers to the fact that the sentences considered there do not have both a subject and a verb (and aren't coordinations of sentences that do).

(I've borrowed from this answer of mine.)