Luke,
I think FOX reproduced just Line Regiment glengarry badges, but could be wrong. Nonetheless their copies were using dies that were not that old and were not worn out, just no longer used.
The age on this badge is reproduced chemically. Blackening loops is simple with gun black and other such things.
See here for another on ebay, this time described as West Riding.
https://www.ebay.co.uk/itm/39th-WEST...UAAOSwH3haJvE5
I show this to compare the quality of appearance on the ebay one as opposed to the one on here.
I make no judgement on the seller or authenticity!
regards