Antique Pearlware Shaving Mug - Odd Shape?

I am hoping to find out more about this unusual shaving mug, because there don't seem to be any quite this shape online. I have seen many photos of some with the holder for the brush on the outside, but not inside like this. The blue and white print looks like it dates from about 1800 – 1830, and I am searching through my books for the manufacturer, but in the meantime I hope you can help me with a few things. What was the purpose of the divisions? It looks like the circular hole, which is open to the area underneath the divisions, could have been used to somehow rinse the brush, or maybe the razor, if it could be manoeuvred down into some water underneath, but it seems rather awkward. The print wasn't made specially for the mug, it is just three identical pieces roughly joined together, so maybe this design was not successful and not worth having its own print.

Any information welcome!

The diameter is about 5.2ins, 13cm, and the height is about 3.1ins, 9cms.

 

It looks as if it were originally lidded.

Debora

 

Thanks, yes, I think it probably was, given the shape of the rim. Probably just neatness, and maybe it kept the flies from exploring any suds left behind!

 

Valuable if hand painted, but I saw a hairline

 

I suspect the hole allows for hot water to be poured in. Check out "scuttle mug."

Debora