100-500 usd
There was no 300 Winchester Magnum cartridge in 1939. A 1939 Model 70 would be marked "300 Mag"...and it will be chambered for the 300 H&H Magnum cartridge. There was no other 30 Magnum cartridge in 1939 in the Model 70. The 300 Winchester magnum cartridge was introduced in 1963,...the last year the Pre'64 Model 70 was made. Your 1939 Model 70 may have had a later barrel swapped in to it. 300 Winchester and 300 Win Mag are the same cartridge.
300-1000 USD what if the gun is pre 1964
Yes--I have a friend who has a 721 chambered for 300 super mag
1 in 10
100-400 USD
These range in price from 250 to 300 dollars and up,depending on overall condition.
Depending on the exact configuration, condition and age, price range of a few hundred to a few thousand.
1 in 10 inches
$500.00 80% or better
If you are asking what was the sn of the first post 64 Model 70 in 300 Win Mag, you will have to gain access to the Winchester records to find out.
50-500 usd