I think I have noticed something about the Copper Cuffs. The database says its class is copper, but..
When I compounded Copper Cuffs+Copper Cuffs, I got a Cloth Hat which is obviously a flower. Then I mixed another Copper Cuffs with the Cloth Hat I got (in this order), failed and got a low level flower as a result.
Moreover, somebody added a following formula (haven't tested it myself though):
Water Bracers (flower!) + Rock Ax --> Copper Cuffs

It seems that Copper Cuffs class is not copper, I'd say it's flower. Or maybe flower/copper, since the Rock Ax is copper/wood and cuffs type items tend to have flower as a secondary class (base class in this case?).