I have a 1975 BSS 20 ga in very rough condition ...

I have a 1975 BSS 20 ga in very rough condition metal and wood but functions flawlessly....28 inch mod/imp cyl. What is the value?

my refrence books say that the BSS Browning was made from 1978-1987 in japan by BC Miroku,,value in rough condition(POOR) would be around 300-400,,then it jumps to in (FAIR) condition to around 600,,early models had non selective triggers and later models had selective triggers ,,
bigcurt