This is a Mole Richardson Female 3-Pin Stage Pin Connector. It has floating brass pins designed for terminal with 2- 50 Amp fuses - one on each hot leg. Black, high impact phenolic shell, heat resistant to 93° C continuous, 121° C intermittent.
It accepts S #10 AWG, SO #6 AWG, and K-Fiber #10-6 AWG 3-conductor wire.
60 Amps, 250 Volts, AC or DC
6.5 x 3.5 x 1" (16.5 x 8.9 x 2.5 cm)
Mates with MC267G.