This is a generic high speed photometer operating in the IR, several of which were used at various observatories in 
    	the latter part of the 20th century. The detector material is not specified in the literature. However, we can say this 
    	is NOT an indium antimonide (InSb) detector which was a common infrared detector material in wide use at the time. 
    	The nominal wavelength range of this instrument is centered on approximately 880 nm which is inconsistent with InSb.