Model: Booster meter
Price (new): tbd
Cell type: CdS
Measuring Range: EV -4.5 to EV 11 (Pellix); EV -3.5 to EV 11 (FT); EV -3.5 to EV 10 (FTb)
Batteries: 3 1.3V M20 mecury batteries—two for the meter and one from the camera.
This is not a stand-alone meter, it's a low-light-level amplifier that fits onto the accessory shoe of the Canon FT and Pellix QL cameras. There's an updated version to include the FTb camera. As far as I can see, none of the other F-series cameras were plumbed for it. Canon did offer a Booster-T finder for the 1970s-era F-1. If I ever get one, I'll add it here.
I think this is pretty slick. It sits on top of the prism and clips to the accessory shoe. It takes three batteries. Two are for this meter and they run the sensor and amplifier. You use the camera's battery to run the meter's dial lamp.
To install it, you clip it onto the accessory shoe. Pull the plug out of the side of the meter. Unscrew the battery cover on the camera and remove its battery. You plug the meter in there. Then you put the camera's battery where the plug was located on the meter body and screw down the battery cover. Now you're set. It's a nice system—it would have been easy for Canon to design it so there's no place for you to put the camera's battery and cap, which means they'd get lost very quickly.
Flynn Marr Photography has a nice write-up on this booster, and they have the PDF of the manual available as a free download.