A  G.L.C ( Greater London Council ) London Fire Brigade 1965 to 1988 chrome error badge issued in the late 1970's & early 1980's. I can confirm this as i am aware only one batch of chrome badges were issued in error as opposed to the normal gilt variation, i myself was issued one in 1980 as my 1st cap badge ! 
The cap badge has an obvious chip to the top right part of the enamel but the centre is securely fitted to the standard economy issue, lined Marples & Beasley Home Office Star, the standard slider cap attachment complete to the rear of the badge & shows definate signs of being worn on a cap at some stage in it's life. Could it be my old one i ask ;o) !