This is a nice wooden extension rail, mahogany, I think. It is in good shape, but is missing the small brass plate that keeps the attachment screw from falling out when not attached. Still would work fine though.
Not sure for what camera, but similar to Kodak/Eastman. 2 slots in the sides. There's a small index plate that has a "1" mark on it. Measurements: 6.25" wide, 9.75" long, .875" (ie 7/8) thick.