This is a vintage DC laboratory micro-ampere meter. This analog, mirrored scale meter is made by Rawson Electrical Instruments, Company and is type 507. The meter has a single range of 0-5 micro-amperes. There are two knobs on top. The left controls zeroing and the one the right clamps the movement. Dimensions are 5X5.25 inches and 2 inches deep. The black crackle paint is beginning to flake off but otherwise is in nice condition.