Bought at an estate sale approximately 5 yrs. ago. Is it considered sponge ware?

Hi it's 5" tall and the opening is 2 1/2" with the width at about 3 1/2". It reminds me of crockery but has a dark brown inside. Looks to have a mark or signature on the bottom. In hand it seems old. Any ideas on it. Thanks so much for any help in identifying it.