I'd have to agree that MAGNETIC snaps with the
Coach name on them especially on older items are probably fake. I've seen what I believe are very early genuine ones with no stamping (someone mentioned a few days ago that the patent information was on a paper sticky in the inside pocket?) or with legitimate company names of the snap manufacturer or just with the US Patent numbers. Some fakes use a cheap magnetic snap with fake (too few digits) patent numbers.
The smaller pressure-type snaps used in most wallets have often been faked with the Coach name. Those probably shouldn't be used for authenticating.
The green wallet with the fake green bag that Etsy seller
RedTutuRetro has listed is probably fake based on both the fake magnetic snap with the Coach logos and on the strange zipper pull but better photos of that pull would be interesting.
It's also important to keep in mind that, just like with YKK zippers, a fake item can still have a genuine snap when the snaps are make by a legitimate manufacturer that sells to anyone who can pay for their merchandise. And with the pressure-type small snaps, finding an unscrupulous supplier in a third-world country willing to make fake snaps with the Coach name on them is no problem for the fakes-makers, just like finding faked Coach-stamped O-rings, strap clips, grommets, zipper pulls, etc. As we've said before , "Anything a maker can make, a faker can fake".