Current prduction since 2005: $400 - $1,200
older production varies greatly, could be much more (see blue book of gun values)
what do you want for it
Take it to a gun smith.
It will be marked on the barrel
Check the receiver
100-300 USD or so
100-1000 USD
Mossberg in the 1970s
Western field 12 gauge single shot shotgun serial #82719 x G...age and value/
100-225 USD or so
100-300 US Dollars.
100-400 USD
its a 1910 16 gauge not a 12