1977 10p stamp silver proof

i have this- its a silver jubilee 10p stamp replica,

my camera isnt working but its the same as here

http://cgi.ebay.co.uk/1977-ROYAL-MAIL-SILVER-PROOF-10P-JUBILEE-STAMP-/180301646434

cant actually find any more info on the web, so if anyone had anything itd be great

thanks