If serials, labels, shell colours, manuals, mfg dates, cases, visible parts of PCB (mask colours, pin size/count and the like can change) or what not are not available then you might have some means.
You might want to visit speed run forums -- those guys usually have to pay far more attention to this sort of thing. Some popular games might also have things http://www.zeldaspeedruns.com/oot/generalknowledge/version-differences
TCRF has a few things for some gameshttps://tcrf.net/The_Legend_of_Zelda:_Ocarina_of_Time/Program_Revision_Differences
Find that sort of thing and it is easier to ask sellers to go somewhere in a game and do something than maybe open a cart or have to find out something more specific.
Also hackers do not tend to just go for the latest ones. Reasoning usually runs something like
1) Other hacks I might wish to incorporate or others might use. Granted this is usually region rather than version.
2) Is it the version I have in this ROM pack? A lot of v1.1 or whatever versions get found and dumped somewhat later in life, and might not be spread as far.
3) Does my save work with this version? It is the reason I have chosen certain regions before, again usually more region than bug.
4) Are there any traits I can abuse? I am told the French version of Ocarina of Time has a larger script than anything else, a lot of hacks will then make use of this.
5) Possibly higher in the list but are the bug fixes good ones, or can I fix a bug and use an earlier version while I am at it because why not. In many cases I would rather mess around with 10 bytes of assembly than reinsert graphics or something.
Frankly though other than "find someone that knows and find a simple to get to visible, audible or playable trait" I am not expecting anything if you have to ask randoms on the internet to do something. Make it short as well -- if I am only selling a $30 game (assuming it is higher end) I can't be bothered to do much where I might well do something special if I am selling a $200 car part or piece of machine tool or something. It need not necessarily be something they can tell and you might be able to ask someone to record some audio or some video as mere mortals often have suitable gear you can then try things on your end with.