Signedon front: THERMO-LAB INSTRUMENTS INC.
on silver label on back: THERMO-LAB INSTRUMENTS, INC. / SERIAL NO. / 213-H-161-BT / 1312 WILLIAM FLINN HWY. (RT. 8) / GLENSHAW, PA. 15116 / MADE IN U.S.A.
FunctionThis is part of an instrument that measures the amount of oxygen dissolved in a liquid. The instrument would originally include a probe that would be submerged in the liquid (now missing) originating an electrical signal that the case translated into a reading on the indicator.