Universal Geneve 884100 has a 36.mm stainless steel case, 20mm lug width, and what I think of as “normal” lug shape. Given the Universal Geneve Caliber 125 is based on the Valjoux 23, we see the pusher at 2 o’clock slightly closer to the crown than the pusher at 4 o’clock.
There are few of these pieces known, and just a couple where I have seen the engraving on the caseback and inside caseback.
There is no symbol on the caseback, only etching at bottom, centered:
884100/02
followed by the 7-digit case number.
There are no ‘ marks in between thousands/millions, as we see in some other Universal Geneve pieces of this period.
A number of pieces appear to be lacking any etching on the caseback, likely due to polishing.
The inside of the case has a circular polish with stamping horizontally centered:
ACIER
INOXYCABLE
[Universal Geneve logo]
SWISS (in larger and slightly different font)
It is common to see the text not centered vertically, and also not parallel to the UG symbol or other text.
Bezel is plain steel with no markings.