Dating winchester 101 trap gun
In this picture illustration of the forearm below, the type 4 is on top, you can see the coil spring for the RH side.You will also notice that this forearm has the later finger grooves on the top edge of the wood.1/8" hole in the front for a retainer pin that the cocking lever pivot pin went into as a anchor for this spring.
On the right are the forearm iron assemblies removed from the wood.
The 4th type used coil springs for the mainsprings, ejector hammers and the top lever springs.
These coil springs proved quite a bit more reliable.
The Grade I Field is the standard version of the Orion, with a plain blued breech and a pistol grip wrist stock.
It is available only for 12 and 20 gauges, but is otherwise identical to the Grade II Field for game purposes.