Basically impossible to value with what you have provided.
remington 870 12 gague
Receiver
gague
all you have to do is look up the answer on goggle and get the answer right away
1971 model.
Your winchester model 101 was made in 1966 by winchester.
Can't be answered without a detailed description of all markings, finish, condition, etc..
100-350 USD
No published sn data. Seldom more than 115 USD
14g
I'm not sure, perhaps it is... RAIN.