Yes, they are under the rear sight.
I see circles with different things in the middle of them, some letters, and other symbols I don't know how to describe. Some circles are smaller than others. One looks like a "K" or maybe an "R", inside the circle. I also see a "U" or possibly a "J". I also see a diamond with a "U" or "J" in it. It is hard to determine, sense the markings are partial, because of the tubular shape they are stamped onto. There is also a seven on its side stamped over top of some of the circles, others, just by themselves. There are a dozen stampings total on the left side. There are also sideways "V"s stamped like corporals bars, one above another. There are also more on the right. I don't have access to a digital camera, or I'd post a picture.
I don't suppose there is a list of Soviet serial numbers, and where the rifles were sent, available to us, is there?