I have a flask marked "Bailey, Banks & Biddle" and "Sterling" but the back side of has a light yellowing / gold along the edge that will not go away with a silver polishing cloth. I assumed that it was sterling since it was stamped sterling but my boss is wondering if its sterling overlay. I tried to find other flasks by BB&B and I can't find any. I know that Gorham made some flasks for them but the only other mark on the flask is 3 shapes along the rim but there aren't any letters inside of the marks. Sorry that it is not a clear picture of the marks but I couldn't get it to focus.
I found a BB&B sterling silver tray online that had 3 shapes like this but they weren't the same shapes. (it started with a diamond shape).
Can anyone tell me why the discoloration won't go away if it is stamped sterling?
Thank you

