This is a front swivel for a target rifle. The screw fits the threaded adjustment base found on the forearm of the model 70 target stock. All swivels are original Winchester parts.
The early pre-war swivel and nut are nickle plated. The later post-war swivel and nut are blued.
We use the NRA Modern Gun Condition Standards Grading System for grading part conditions. You can read about it HERE