Posted By:
hankronBuying online, it's best to buy raw 1951B Mantles from reputable dealers. There are a lot of reprints and fakes. However, if you've seen a lot of legitimate Mantles (even if only online) many of the fakes look obviously bad.
For in person, you should buy a number of cheapo 51B commons for comparison. The key with the 51 Bowmans is that they were printed on coarse dark grey cardstock. Many reprints will have white edges or otherwise goofy stock that quickly give them away as fakes. If you have some cheap commons with you when you go to a show or whatever, the fake Mantle will standout like a sore thumb.