The Flame logo was introduced late 1973, used until circa '79. It was gradually phased out from '78 though, to be replaced by the flat polished bases and the triangular black sticker, though the phasing out happened more with the Azurene bits than others.
(Mark Hill, p.134.)
This tortoiseshell design was a continuation of the design developed by MH at Mdina.
Nice bit Ivo - I've got a similar big one, but it has a big crack in it's base. Still displays well though, and cost me less than Â£20.