Definitely not a sopranino. I have a bunch of sopranino mouthpieces most are around 5 cm in length. Soprano mouthpieces are around 7 cm. Yours looks closer to 8 cm so on the large side for a soprano, but probably not an alto. Just a rather long soprano mouthpiece. No idea of the maker and may just be a Chinese unbranded that's thrown in with cheap new instrument? Have you played it? A soprano reed should fit.