I noticed that the name of the photo was Win63, so ... is this an Argentine knock off?
You got it!
I know Colt, I think S&W, and I've heard Winchester, all licensed Argentina to produce copies of certain firearm models.
Your rifle is the first Winchester I've seen. I'd take an educated guess and say the stampings on the stock are military, as all firearms there go through them, as well as ammo sales.
Model 63 parts will interchange, and it looks like you need a rear sight. Give me a couple of days(I work insane hours), I think I can track one down for you.
I'll also run this one by my Winchester expert buddy, and see if I can get some more info on it for you.