This carbine is an Iver Johnson M1 carbine, sporterized model.
The rear mount screw has been drilled and tapped through the rear sight V notch. The front mount screw has not been drilled and tapped. It's a set screw. The mount looks like it's held in place on the front from pressure exerted from being wedged between the stock and receiver.
This carbine is for sale on Gunbroker at:
http://gunbroker.com/Auction/ViewItem.asp?Item=86608105
I have e-mailed the seller and asked for better pics of the mount and who made it.
Mike, I realize it doesn't have the 2nd hole, but this is the closest I've seen so far. Maybe the same manufacturer?
Jim
Southern Cali
BavarianM1Carbines.com