Oh, yes! Thank you so much for all these! :) And yes, surely a tombstone, or fragments of more than one - I can see "hic iace..." in the second photo, which looks a lot like the beginning of "hic jacet [whoever]", i.e. "here lies [whoever]".
Are all the pieces parts of the same original stone? I'm puzzled by the upside-down triangle in the first photo; is it an ordinary letter in a form I don't recognise?