You may have an original sporter, the stock of which had to be replaced for some reason. If so, returning it to military configuration, which would involve installing a rear sight on the barrel, should not be an option.
The rifle appears to have a sporter barrel, which is larger than the issue Springfield at the breech and lacks the cut for the rear sight spline. It has the same profile as the M1922 barrel.
I may have a special sporter buttplate which could be used to replace the rubber pad. I will check it out and PM you.
