The Universal Geneve 881101 is powered by the Caliber 281, first produced in 1933/34 by Martel. This is both the first caliber to use pushers at 2 and 4 o’clock (est 1933/34), and the first full calendar chronograph that has four subdials (1942 the first with date, then adding the full calendar and moonphase in Tri-Compax in 1944).
The 281 features specifications including a Breguet hairspring, 17 jewels, running at 18,000 vph (vibrations per hour), and a power reserve of 36 hours. Although some sites note that the movement was produced by Martel for Universal Geneve and Zenith, Universal Geneve has confirmed that they produced the 281 components and movement in house, and in the case of Zenith, some components such as bridge or levers, were modified by Zenith. [1]
Within the Clapton we see a single stamping design on the chronograph bridge:
on the branch for the chronograph/center wheel jewel: UNIVERSAL GENEVE
on the branch for the minute register wheel:
SEVENTEEN
17 JEWELS
UNADJUSTED
and then SWISS just below the screw.
The only import code seen is HON, indicating U.S. Importer A. Hirsch. Not all pieces with English Day/Month discs have the HON stamp, but all movements I have seen with an HON stamp use English Day/Month discs.
[1] Universal Geneve, email May 10, 2020