The Royal Scots officer’s with blackened finish 25mm

A post 1881 button which carry the regiment’s  name THE ROYAL SCOTS whereas the earlier 1855-81 button was titled THE ROYAL REGT. The 25mm button is in good condition and has the backmark  FIRMIN  LONDON. We have not come across a button of the regiment before with this very darkened finish. It was most probably have been worn on officer’s service dress of European or tropical style and may be as late as WWI: its difficult to be precise with buttons without crowns.  may22/4