Anne — unfortunately I don't recognise the pattern on your SOS cube sugar.
My two are:
Davidson — Fostoria
American /
Georgian pattern in flint, also made in jade (1931-34). SOS lid marked "LLTD" on the side of the rim in relief, in a wide shield-shaped frame like a hallmark.
Walsh — as Reynolds fig.118 (i) which shows a conventionally metal lidded preserve jar with two rows of the pattern; this SOS cube sugar is lower and has just one row. Identical SOS lid except marked "W L° C" in the first shield-shaped hallmark and then in a second rectangular one "A". The tiny "O" in this mark could just be a badly formed "D" for Ltd.
I have looked for possible makers in Mappin's EPNS marks, but there are no obvious candidates.
Bernard C.
