Having been in factories that make all sorts of ham I don't actually eat it myself, DP like wafer thin ham for his sandwiches but has banned me from talking about what it's made from. Wouldn't give it to DD though.
Wafer thin of cheaper square ham is made from the offcuts of other hams, it's still ham just not top end quality, it's mushed together with salts and water etc to bulk it up a bit and cooked in a giant sausage hence the shape. With "nice" ham it's cooked on the bone so still resembles the pigs leg.
Haven't come across turkey ham though in my travels but am a bit dubious.