I've just bought this dish which has the same design as the No. 18610 rectangular one shown on P.3 of the Hermanova before 1958 catalogue on Marcus Newhall's CD. This one is 16cm. in diameter and I assume is for butter etc. The question I'd have is, is it part of the same design suite as GTS Mystery 145? It seems to have the same finial and ridged lid and the flower/sunburst on the base.