The hollow underside to the 'wings' is a little odd, but I haven't seen enough of them to form a judgement. Perhaps these were a later production when they redesigned the outside as well?
The two flutes (yes, not gooves) are 7/8 (22mm) long on mine, not sure what you mean about the gully, but the distance from the flutes to the edge of the lip is 5mm.
The difference in colours I can't answer straight away but they could vary. The darker hue might just be a different mix – and there are several colour variations of this ashtray. I'll see if Ray Drury knows anything about the pre-war pressed glass (there ain't many other people left!) and how many different pots were in use.
Sizewise it conforms perfectly, so I'm pretty sure we are on the right track
