Indian? western? belt buckle solid silver or plated?

This belt buckle was purchased in 1957 or 1958 on a family vacation to Montana. As vacation souveniers my brother and I chose to have leather belts hand tooled with our names and this is the buckle that came along with mine. The belt and buckle came from a leather shop in Missoula. I believe it resembles something similar to Navajo Concho buckles Iv’e seen online. It measures app. 3" x 2.5" and weighs 1.2 ozs. on my postage scale. It has very dark tarnish as I have not polished it for many years. The only marking on the buckle is an AG that can be seen in enclosed photos. I am trying to determine what this buckle really is. Some type of solid silver or plate. It is not marked sterling which would make it simple. Just the AG. I did obtain silver test acid and filed an area on the buckle back and applied the acid. The acid did not foam or turn light green but remained reddish brown colored. The buckle hook and barloop where the belt attaches along with the solder do turn light green and foam.

I did have a local jeweler take a look at it and he quickly gave an opinion that it was just commonplace inexpensive plate. He did nothing as far as testing. I also had a local gold and silver merchant look at it and he too gave a very quick uninterested opinion that it was some kind plate. I have not given up hope that there may be more to this. The fact that an AG has been stamped into the piece and my scratch and acid test seemed to rule out plating is why I have come to this forum for second and third opinions or suggestions for further investigation. Or maybe you knowledgable forum members will also tell me this is just an inexpensive commonplace piece of STUFF.
I appreciate the opportunity to post my questions.
Thanks Dennis
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