Bullers 2542
This example is clearly stamped with a 1944 dated Bullers logo and what I presume to be a pattern Number, 2542, on the reverse face.
The spindle, not shown, appears to be cemented in which seems unusual for such a late dated insulator
As per most Bullers insulators of this date, the inner shed is recessed.
It is similar in dimensions and style to a large Terminator though obviously shorter due to there being only a single wire groove
Another very large wire groove cuts across the top which is quite unlike a P1600 which has a much smaller, thinner groove
American collectors have classified this insulator as possibly U-1718, though I need to confirm the dimensions.
Update
The U-1718 is dimensioned at 3.1/8in by 3.7/8in whereas this example measures 3.1/2in by 4.3/4in also it seems to have a deeper wire groove. Therefore I presume it is not a U-1718 but a new pattern maybe.