Copper/Bronze with silver toning? Thai 1 Att

Hi all, a little assistance required here if possible on toning?
I have been trying to get to the bottom of these Thai 1 Att coins and why they have quite a strong sliver toning to them. They are dated 114 (1895), Reign of King V Chulalongkorn. It would appear they have been displayed at some point as they not only have been pierced, but it's almost as if they may have been silver coated in some way - unless this type of toning/colouring can happen with copper and bronze coins? Has anyone had experience of this colouring taking place in similar coins, only I have searched the net and cannot find anything similar apart from a 1 Att pattern strike that was made in nickel:
https://en.numista.com/catalogue/pieces33334.html
I also have a few others with the same silver colouring and holes that all came together, but some are dated slightly later (1875 -1873). Thank you for any help in advance.

Hello and welcome to Numista!

It looks like they were holed and plated for jewelry. It's easy enough to learn how to plate coins:

https://youtu.be/_g_ml8tAnWE

Agreed, they have been plated and rather than toning, what you can see is where the plating is wearing off and the bronze is showing through.

Thank you very much for the info here. I apreciate you taking the time to help out here. I thought it was a weird natural colour for them to have gone. — Does this mean, what with the holes and plating, there will be very little numismatic value left in these coins?

Thanks.

Unfortunately, yes ─ no numismatic value.