Matte Box with bellows measuring 4x6 inches. Not sure about the brand, but it was together with Arri 16mm movie equipment. The rear mount ring measures 60mm diameter on the outside and 57mm on the inside. The rail in 7.5 inch long.
There are 2 60x80mm rectangular drop-in slots for filters in the rear. Overall looks to be in excellent condition for its age, works well, with no serious scratches, no dents. Bellows are in excellent shape with no holes or tears.