The 250 would date to 1951, the 358 to 1956. The 250 would be factory drilled if it's a 99R but probably not if it's an EG, the 358 was definitely done at the factory.
Basically, if you can see the Savage Model 99 stamp on the front receiver ring then it was factory d&t. If you can't see it, then the stamp is on the top of the ring and hidden by a scope base and it was d&t after market through that stamp.
Factory d&t like this: