http://www.usedprice.com lists the models below. However, I would not consider this definitive as they seem to just collect information from other sources and are not experts in melodicas by any means.
Hohner HMS-32, 2005
Hohner HM-32 Piano, 1978
I assume the HMS-32 is the current student model (s = student). So there is no other listing for 32s.
Other Hohner models are listed as well.