http://www.ebay.co.uk/itm/George-VI-Silver-Crown-1937-Coronation-Frosted-VIP-Proof-Crown-S4079-FDC-PR65Cam-/172878995156?hash=item2840641ed4:g:hsgAAOSwHtFZxMop ???? have 2 of these crowns frosted like this, do i need to get them slabbed or is the seller a bit optimistic