HIGHLY improbable that it's a fake. More likely the stock was repaired in service at some point and a later nosecap was used.

FWIW, I also have a 31 with a one piece cap. It's not uncommon.

The main thing to look for is the finger groove on the bolt handle side of the stock. Should be a cartouche there with SYT in an oval. If it has that, it's the original stock and worth a pretty penny