Hi Dave,
Welcome to the forum, as Alan says the badge came in a blackened brass variety so is best left as is. I believe yours is a restrike I'm afraid, my uncle has a J.R.Gaunt marked brass one which is certainly a restrike and yours appears to come from the same die, if you look at the '0' of '0f' (in the 'county of London' title) its very oval and noticeably askew to the left the further up the 'o' goes. Sorry.
Cheers,
Luke
incidentally if you are looking for a genuine one:
http://cgi.ebay.co.uk/ORIGINAL-19TH-...ayphotohosting