It's very easy to distinguish a pre-'64 Model 70 from a later model. The early M70s had an external claw extractor like a Mauser 98. '64 and later eliminated the claw extractor and instead use a small extractor internal to the bolt face. The claw extractor didn't return until a couple of years ago after FN bought the Winchester brand.
If indeed you have a pre-64 in reasonable condition, it's worth a tremendous amount of money. If it's post '63, then it's not worth much, which is not to say it isn't a perfectly good gun.