99EG's didn't have monte carlo buttstocks. Nothing did before 1960, so if the serial number is under 1,000,000 that would indicate a replaced stock.

Now, it's possible it's a factory replaced stock.. but could also be aftermarket or swapped around by an owner.

If the serial number is over 1,000,000 or starts with a letter, than it could be a 99DL with monte carlo stock.

An EG will always look like this, and later ones do have a jeweled bolt