Anschutz 1413 reciever stamp question.

[bored184]

I am trying to figure out why my Anschutz has an A stamped on the receiver. I've tried this question on another forum and as of yet no one knows why. Using the gun auction sites as a photo reference I have yet seen one with an A on the receiver. However some on the other forum have referenced having an A stamped on there receiver. It seems like some rifles have them and some do not. Below is a photo, its a 1413 Supermatch dated 1973. Any ideas?