The Fed-4 were produced in two versions. The first model (reffered to as Fed-4 (a)) has wind knob and was modified from Fed-3 (a) to accept a light meter. The Fed-4 (b) has much higher viewfinder assembly to add a light meter. The light meter control knob is where the rewind knob was so the rewind knob now sticks out of the side. The Fed-4 (b) camera again was available with either single or dual lettering [2].
Produced: 1964-1971
Name: „ФЭД-4“
Producer: FED
Frame size: 24x36
Lens: Industar-61 2.8/52.
Shutter: 1s, 1/2s, 1/4s, 1/8s, 1/15s, 1/30s, 1/60s, 1/125s, 1/250s, 1/500s + B.
Quantity: 633.096 units (all types). (sovietcams.com)