This rare SCHNEIDER Kreuznach XENAR 3.5 150mm / 15 cm dates back to the mid to late 1920s and was originally supplied with an early Linhof Technika camera (now sold). I believe the design is a Tessar arrangement with uncoated elements and it certainly has an unusually fast maximum aperture.
Made for Wallace Heaton No.2 f4.5 ANASTIGMAT ZODELIAR lens (non focusing lens to fit camera with bellows). IRIS OK. The engraving on the lens is very hard to read due to age. Should work but optics do have marks.