Small crystalline vase with 25 mark

Wondering if this is a test firing but would love to know the makers

Looks to be a nice European crystalline vase from the 1930's, the 25 is probably the shape number for that vase. If it is any newer it has had a rough life as that base indicates some age. I can't give you a maker there are not many reference books on European ceramics from the first half of the 20th century, most tend to be factory or era specific like and of course not in English. I would guess this is French, German or Austrian and made for the home mark due to the lack of country of origin.

I love these experimental glazed pots but rarely can you pin down who made them (unless like most English ones they say).

Could it be California Faience? The glaze technique looks similar and I think I read somewhere that they may have collaborated with European factories.

The base and the number look right for Pierrefonds pottery, and they
did specialize in crystalline glazes.

I see what you mean, but all the examples of Pierrefonds that I have found have three figure numbers all in one line and with no serifs. The US shape numbers are mostly 2 digit.