No serial number = no way to answer.
Yes, Browning made the B80.
1981
Download a manual from Browning or take it to a gunsmith
Best left to a gunsmith
100-400 USD
50-500 usd
Best to ask a gunsmith for help.
Not sure if it is a B80 or an A500, but it was made in 1988 in Europe (not Japan). Depending on which model, $400-$500.
Depending on condition, from 250-450 USD.
$250-500 depending on condition
$250-500 depending on condition
You need to see a gunsmith.