How can you be sure a pocket watch case (American sizes) will fit?

[RLang386]

So the other day I got an Illinois Bunn Special in pretty rough shape for a whole ten dollars. No case back, hands or crown, snapped winding stem, plenty of cracks in the enamel, crystal gone, bezel stuck--but it (barely) runs when manually wound. So I forced the bezel off and I am now the proud owner of a pretty decent American watch movement (23 jewels and a motor barrel!) with no hands or case. Boy was it dirty under the bezel, too... but it has a Montgomery dial, which is always a plus for me, and it's lever-set!

I'll service the watch later, when I'm competent to, but it raises an interesting question. I see from pocketwatch database that it's a 16s diameter. But this says nothing of the thickness/"height" of the movement.

My actual running pocket watch, which I do sometimes carry, is an Elgin Grade 290, a much less expensive pendant-set hunter movement from about ten years earlier that is also size 16s. But the Elgin is substantially thinner--with back and crystal the case for the Elgin (a nickel Wadsworth case, if you're wondering) is about the same height as just the Illinois movement.

I want to buy a case and hands--the hands I imagine are pretty easy, since people seem to buy watch hands all the time in restoration videos, even for 1900's pocket watches. But how would you know from an online listing that a case of the proper diameter, with the little thing milled out for a leverset movement (usually visible in photos), would be for the right "thickness"?

Any other advice for buying case, hands, etc is welcome!