exact items shown, a test set pair, the 736C transmitter and the 836A receiver - from Western Electric Lightguide Systems.  The original batteries, thankfully, had been removed before I got these so there was no leaking battery corrosion.  as you can see, they are very clean, battery voltage between 6.3 and 7.5 works, I used a bench power supply that I ramped up until the battery low light went off and the battery good light came on.  The test probe that comes with the receiver clamps around a fiber cable, either single strand or ribbon.  I used the laser in the transmitter for my testing.  I set the laser to pulse and as you can see in the video, as the laser ON light flashes on and off, the power receive meter on the receiver is moving up and down in synchronism.  That's a pretty convincing demonstration that the pair is working.  The laser is infrared, but I don't know what frequency.