This might be older than C20th but you'll know more than me

I can't find the little square-ish mark anywhere and don't know anything about this odd little pot. Can you help? Thank you!

Very typical lidded toothbrush box/holder that almost certainly would have come as part of a toilet set - jug, basin, soap dish, etc. The style of decoration and lustre would suggest 1860s - 1880s. I doubt that diamond mark is anything other than a factory batch mark, while the number is the pottery's pattern number. Quite probably Staffordshire. I've seen these described as razor boxes too (but I don't think they are!).

Thanks Essenjay. Do you think it could be Minton because their 1857 mark is a square like that.
And do you know why it would have the embossed number as well as the painted number?

Hmmm, it's possible - the quality looks okay but, as far as I know, Minton usually marked their stuff. The impressed 40 is probably the factory number for the shape of the piece and the painted number the pattern, a system that can be seen on pottery until at least the 1980s and probably beyond.

Thanks essenjay. I've googled toothbrush holders now so am a weeny bit wiser. Didn't see one like mine though.