Audio Research Corporation, Minneapolis, Minnesota. Pair of monaural model M300 MKII hybrid audio amplifiers. Serial numbers 87136010 and 87136015; with manual. Tested as working. Originally manufactured in 1988. The then-new technology allowed for the hybrid utilization of Field Effective Transistors (FET) with vacuum tubes to allow for the best sound from both devices. Rated for 300 watts. Each weighs approximately 110 lbs; total weight of the lot is approx. 220 lbs. Each, height: 10 1/2 in x width: 19 in x depth: 18 1/2 in. Weight, each: approx. 1a0 lbs; gross weight of lot: 220 lbs.