I think it's better than a
reminder dial. I think the K773 has an 'electric eye', that is a light cell (I think selenium) which should give you auto-aperture. The knob offsets the meter circuit for the sensitivity of the film. ASA is the same number now usually given as ISO.
I think the camera is for 'standard 8mm' film; that is, 16mm film that's run through the camera once, exposing only half of its width; then turned round and run again, exposing the other half. The film processors split the film along its width, so what you get back is 8mm film with only one set of perforations.
You can still get film in this standard, but only just: Fotoimpex will sell you one type of film, which is inconveniently ISO 100 black-and-white:
Cine film Double 8 and 16mm For all 8mm cine-film cameras with film reels (that is, not super-8 cameras). 100 ASA panchromatic film. All Fomapan 100 R films can be ...
In the US, Blue Moon keep the same stuff:
Blue Moon Camera & Machine: Buy Fomapan R 100 Double 8mm Film 10 Meters online or in store at Blue Moon Camera & Machine, Portland, Oregon.
Getting the film processed is another problem. And then you need a standard-8 projector.