Need Help Identifying Vintage Prison / Jail Lock

I have this vintage prison lock and I know nothing about it, I have searched the net for hours trying to find anything about it. The lock is stamped " DEFIANCE PAT APL'D FOR " on the case. There are two marks on the inside of the lock, there is a capital "R" on the inside case and another capital "R" on the bottom of the bolt. I know the last part is patent applied for, but I'm having trouble finding a Defiance lock company. There is a Defiant lock company but I think that it is different from mine. The lock case measures about 6 inches by 4 1/4 inches by 1 1/2 inches, it weighs 5 pounds 11 ounces. I want to find out who made it and how old it is? Also, what kind of value it has? Thank you for your help.