I heard that the plurals of letters, numbers and words could be punctuated - with single quote marks on both sides - in this manner (especially in Britain):
'X's 'd's '5's 'thank-you's 'maybe's 'his's 'as's
I am sufficiently aware that we could italicize the letter, number or word and follow it with an unitalicized apostrophe 's'. We could also use just one apostrophe: x's, thank-you's, maybe's. This makes 'thank-you's and 'maybe's look possessive, not plural. In the two examples I just used in the previous sentence ('thank-you's and 'maybe's), the insertion of a single quote mark before and after each word (followed by an 's') definitively defines the plural of the word as a word. The same logic is applied to individual letters and numbers ('9's, 't's).
Bottom line, is my usage (albeit probably somewhat antiquated) correct?