79th Highlanders (Cameron) Officers Plaid Brooch

[irish79]

Hi, I am researching the pre-1881 officers plaid brooch and was wondering if anyone could help me with any pictures of genuine examples or could help me answer a few questions. I know that the pre-1881 version had "LXXIX" under the sphinx where the post-1881 said "EGYPT". Was the officers version made of silver? When silver was it normally hallmarked? Is there anything particular I should keep an eye out as to fakes? Any help and advice would be very much appreciated. Thank you in advance.