This is a gimbal mount, assuring a pure angular adjustment (no translation) for an optic appropriately mounted (i.e., with its active surface positioned in the plane containing the crossing point of the two rotation axes, picture #1). A special set of ring adapters assure an optic of 50 mm (2") diameter to be mounted precisely in that plane (pictures #2 - #4). Angular range of adjustment: cca. +/-5 degrees. Angular resolution and reproducibility: cca. 0.5 mrad or 1.5 arcmin. Geometrical aperture: 56 mm (2.2"). Used, in good functional and cosmetic condition, made by Burleigh Instruments, U.S.A., cca. 1970 (pictures #5 - #12). For general optics and laser laboratory.