That gun, serial number 50,000, should normally have a flat loading gate, but Ruger had a habit of holding back guns with even serial numbers such as 50,000, 100,000 and so forth. He would use them as present to famous people and gun writers and such. I would bet that that gun was held at the Factory and when it was shipped the Factory replaced the Flat Loading Gate with the Round Loading Gate that was being used at that time. I understand that the Factory would replace the Flat Loading Gate with the Round Loading Gate, shortly after the introduction of the Round Gate, for guns return to the Factory for repairs. So for a gun shipped shortly after the Round Gate was being used, it would be used instead of the Flat Gate. It would be interesting to know the shipping date of that gun.