ORIGINAL: bigbulls
Before you take it to a gunsmith remove the stock and look at the underside of the barrel. Many times the gunsmith that made the rifle will stamp the cartridge it is chambered for on the bottom of the barrel so it is not asthetically displeasing to the customer.
My thoughts exactly. I used to work in a gun shop and we had a few come in like this. As you said many of the had been stamped but were under the stock.