Do a sample test on one pin and stannous test it. If you have access to an XRF, a quick test with it could help.
I have never seen a part labeled with the contents, but with test parts anything is possible. I once pulled a bunch of pins that are typically heavy gold plated to the point they produced results as good as high grade gold filled. Only these came out at around 18k solid gold. All I know about the boards is that they came from a hospital that was being tore down to be replaced by a more modern one.