Spotting Genuine 30’s UG Monopushers

Hi all, watch newbie here.

I fell in love with those 1930s and 1940s monopusher chronographs with snail-style tachymeters. I can’t explain it, but there is a consistent design across many different brands (UG, Longines, Landeron…). Yet, in a single brand, I can’t find two watches that are 100% identical as there will always be a more or less obvious difference: case size/style, typo, logo size or style, watch hands…
For instance, here are 4 pictures of UG attached to illustrate those differences. In that environment, how do you guys manage to spot a genuine watch and a fake/refurbished/redial?

Thanks and have a good day!

Early mono poussoire are amazing. Here are a few examples I have.
Unfortunately the enamel dials are very fragile,hairlines and missing enamel.
Movements are usually early Valjoux,Lemania, Universal etc…
Also parts can be a challenge.

Black dial, wonderful. Bravo