Shimano Deore LX FC-M550 triple chainset. 175mm crank length.
Biopace chainrings 46/36T/26T
Square taper interface BB required JIS taper 121.5mm (122mm) axle length.
The chainset may have been mounted at some point. some of the ones I have received have crank bolt marks behind the dust cover cap but the chainset otherwise looks new and unused.