The ground floor of this two-story brick structure has lately been occupied by a nondescript deli-grocery. The legend inscribed at the roofline belongs to a much older business; the Martens Cafe may have opened its doors early in the 20th century. More, I don't know. A 2007 report on the designation of a Dumbo Historic District didn't pin down the date or offer further details.
Surviving signage at 52 Jay St. (Plymouth-Water Sts.), Dumbo, Brooklyn