Roseba 55

 
Roseba 55

Roseba 55

Description

Roseba, one of the many swiss manufacturers of pin lever movements, which flew a bit under the radar, made this 10 1/2 ligne pin lever movement with a Roskopf-type construction, which stands out because of its odd position of the balance cock.

base plate

base plate

In the version shown here, 17 jewels were used, all bearings contain rubies, but unfortunately, there are also competely useless blind jewels on the dial side.

mainspring barrel with slipping clutch

mainspring barrel with slipping clutch

As usual for a Roskopf type movement, also the Roseba 55 has got on top of the mainspring barrel a double wheel, which drives both hands at the same time. This wheel is attached to the mainspring barrel with a slipping clutch.

gear train

gear train

The large mainspring barrel overlaps the center of the movement. It is followed by the large driving wheel, seconds wheel and escape wheel. The seconds wheel indirectly drives by its outer teeth the outer teeth of the center seconds wheel.

The empty bearing on 6 o’clock is interesing, maybe it is a preparation for a decentral seconds indication on another version of the movement.

side view of the gear train

side view of the gear train

A simple, non shock-protected anular balance is used, which is beared under a clock, which is mounted near the center of the large movement plate. This is a pretty unusual construction.

empty dial side

empty dial side

You can see, how the lower wheel of the mainspring barrel drives the cannon pinion.

The two cap jewels at positions 7 and 8 o’clock are weird, because they don’t have any function at all, since below them, there are no bearings. So, their only purpose was, to achive the “magical” number of 17 jewels, which should indicate a good quality movement.

calender mechanism

calender mechanism

The hour wheel is driven by the upper wheel of the double wheel on top of the mainspring barrel. It also drives the date switching wheel, which makes one revolution every 24 hours.

Roseba 55: Dial side

Roseba 55: Dial side

The calendar mechanism is pretty simple, the date switching wheel engages with the internal sprocket of the date disc. A spring takes care, that the date disc properly locks after each switching process.

Technical data

Manufacturer:Roseba
Caliber:55
Size:10 1/2''' (measured: 23,0mm)
A/h:18000
Number of jewels:17
Escapement:Pin lever
Balance types: monometallic anular balance (two legs)
Shock protection(s): none
Balance bearing / direction hairspring:Clockwise
Moveable stud:no
Adjust mechanism:Hairspring key
Construction:
  • lever
  • escape wheel, seconds wheel, center second pinion, third wheel, mainspring barrel
Construction type:solid construction
Winding mechanism:yoke winding system
Features:
  • SCI (indirect center seconds)
  • QG (date indication (aperture))
References: Flume: 1962 22
Inventory number:21042

Usage gallery

Mortima Datomatic gents watch  (case missing)

Mortima Datomatic gents watch (case missing)