Good afternoon
Looks like silver to me. Any Jewler can do an simple acid test to definitively show it is silver and at what caret value. The silver will get dissolved at the spot the test is taken so use a part that has silver on it but covered by a stock or other part. The trigger on the back side would be sufficient. I personally would not take the whole rifle.
Also have the jewler write a test statement. I would call around and see how much they charge. Just tell them you have a family piece you want tested.
Mike in LLama Land