I got a FED4 on eBay, mostly because it had an Industar61 lens attached to it, and was therefore a bargain. And, I'm hoping the flash will synch properly. AND it has a light meter, which is said to work.
This is the manual.
I was wondering about the actual mechanics of the shutter curtain, and this has the craic, here. There's lots more useful stuff at SovietCameras.
It's said to be a "beast". Would come in handy for street photography, if set upon.