 bases and reel magazines, was manufactured locally, initially by the American Optical Company and later by Ballantyne.The DP70 consists of a monocoque, cast iron chassis containing the mechanism, which is completely oil-immersed on the non-operating side.Jan-Jacob Kotte believed that the use of heavier materials to absorb vibration reduced instability in the projected image, and this is certainly reflected in the design of the DP70