That got a bite from me 😀 .
Agreed, the Epsilon is not as high quality as the Compur or Compur-Rapid, but for me it does the job if you don't need 1/400 second or a built-in delay timer. I've CLA-ed/repaired a few of each those Epsilons & Compurs of that era, and happily used them all. Of course, on some of the Ensign and Kodak older or 'lower-range' version cameras, the Epsilon may be found omitting the timer mechanism for speeds below 1/25, and having top speed only 1/150.
Once, whilst working on two cameras, I did transplant an Xpres from a Selfix 820 on to the Compur-Rapid on a Bessa Rangefinder as an experiment. It made a perfectly good, and very pocketable, combination.
The Xpres on the Autorange 820 was re-calculated to optimise for colour film, and is distinguished by 3 coloured dots. (You often see e-bay Selfix seller optimists saying that the Selfix Xpres is the same one.) Nevertheless I have always found the Selfix 820 Xpres to be perfectly adequate for colour photography (come to that, so are plenty of pre-1940 uncoated lenses if you take care to avoid stray light.)
I had an Autorange 820 once, I sold it because I didn't like the ergonomics; you have to remember to hold it carefully so that your grip doesn't retract the focus position that you had just carefully set up 😱 .
