Help a newbie garner all possible information for a laser with hull number: ZFS97586M81C

All numbers appear clear with some question about the 9th digit being an "M". Appreciate your support. My google sleuthing resulted in the following:
ZFS - Manufacturer: Performance Sailcraft
97586 - Sail Number indicating 1982
M81C - Not sure?

Look forward to your thoughts including how I can estimate it's value based on condition.

Thanks for your help / support.

Scott