The Jaeger Reference 224105 is a highly coveted, oversized vintage manual-winding chronograph from circa 1950. Famously known by collectors as a technical powerhouse, this rare variant bridges the gap between a professional clinical instrument and a high-end dress watch.
  "Tri-Compax" / Three-Register Layout
  The "Tri-Compax" notation in this context indicates a symmetric three-register chronograph layout. This design provides distinct tracking sub-dials for running seconds, a 30-minute counter, and a 12-hour counter. 
  The Jumbo "Doctor's Watch" Persona
  A diameter of 38mm to 39mm was considered massive (or "Jumbo") in the 1950s. Many original iterations of this reference featured a pulsometer scale printed along the perimeter of the silver dial. This allowed medical professionals to measure a patient's pulse quickly using the sweep-second chronograph hand.

Feature	Specification	Detail
Reference Number	224105	Varied as 224105 or 224105/1
Era / Production	Circa 1950s	Late mid-century vintage
Case Material	Stainless Steel	Highly prized unpolished variants
Case Dimensions	38mm – 39mm	"Jumbo" or "Oversized" for its era
Lug-to-Lug / Thickness	46mm long / 12.5mm thick	Strong wrist presence
Internal Movement	Caliber UG 285	Hand-wound Universal Genève column wheel
Dial Profile	Silver with Tri-Compax layout	Includes a pulsometer scale on select dials
Crystal / Pushers	Plexiglass / Mushroom pushers	True to 1950s period design