as already mentioned here, it's an early Skeet Gun

the 2 firing pins and 2 V-springs come as a standard spare-set with the gun.

the extra trigger group would have to be bought separately -
looks to have been a serious competitor who wanted a quick change over if a spring went during a competition?

the serial number puts this gun into the 1974 range of numbers.

Barrel proof 'XXX' for 1974 should confirm that


rgds
Gunter

NRA Life 1974