This piece is a little bit newer than the [id=473726017;M-2745A] shown previously, and it shows. The whole insulator is trimmed a little thinner to cut down on weight, most notably the ears, and the lower shell is curved on top to encourage better water run-off (I assume). This example is faintly ink-stamped "[P-inside-C] 1942" on the lower side of the top shell. Being a war-time piece, I suppose the thinner construction benefited the war effort in consuming fewer resources.
I haven't seen enough of this style to be able to say for certain what other marking types it can be found in. I have seen unmarked examples.
The glaze on this example is typical of the 1930s and early-to-mid 1940s - a caramel-coloured base with drippy dark grey/black mottling.