I just had another and closer look at the buttons under a magnifying glass. There are numerous scratches on the back of the buttons where the split pins have been inserted over the years. On none of them is there any sign of another metal showing through. I would say they albeit that they are not hallmarked, they are silver. I appreciate that they can't be officially sold as silver without hallmarks, however, this does not detract from the very fine quality of the work in them. I play a solid silver flute, so at least I do know what silver looks and feels like, even if I can't date a kilt!

Greetings on a sunny afternoon in West Cork, Ireland.