Take a look at the link to this Bohemian Groschen, I'm not sure. The cracks on the reverse look suspicious. https://www.ebay.ca/itm/Bohemia-Gro...443364?hash=item1cef558464:g:6FoAAOSwiRBe7OLq
Medieval and early modern pieces aren't really my specialty but in my opinion it looks like a legitimate hammered coin. I'd love to hear other's opinions, like I said I'm far from an expert.
Quite normal for hammered coins to have striking splits. If metal isn't sufficiently annealed to soften it prior to striking, it will split/shatter when worked because it is too hard and brittle. Splitting due to being hit with a spade when dug up is a different matter.
It looks like a Prager groschen, a poor strike like most of the type! Funny enough, the weight of these seems to vary from 2.2 to 3.9 gr, i guess it depends on the time it was struck. I'm not familiar with medieval coins, just had a quick check on ma-shops for comparison, but it's an ugly piece and i wouldn't buy it regardless!
