Bifora’s range of 5 1/2 ligne tonneau movements was very limited: The caliber 51 debuted in 1964 and was four years later replaced by the Bifora 52. The latter got during its short production period of four years, a change on the mainspring barrel and became the one presented here, Bifora 55/2, the final caliber in this tiny size.
One can only speculate as to why it was already over in 1974, perhaps watches, which needed such tiny works were no longer in demand, and maybe, these movements were too expensive to produce compared to the perennial favorites Bifora 91.
Quality-wise, this movement is very well made, all important bearings, including those of the minute wheel, contain rubies. Thanks to the both side ruby bearings of the minute wheel, this movement counts its 17 jewels even without any cap jewels.
Characteristically for the gear train is the tiny triange, which third wheel, seconds wheel and escape wheel reseble. The first two ones are really small, the escape wheel large in comparison.
The tiny size requires a multi-storey construction, in which the bearings of seconds and third wheel are located above the escape wheel.
The balance wheel is a golden tones, two leg anular balance, which is beared in two inhouse Bishock-shock protections, and which already beats with 21600 A/h.
Its frequency is adjusted with a very small regulator arm or directly at the hairspring key.
Of course, a swiss pallet lever escapement is used.
The dial side also offers a very neat and tidy picture, and of course a yoke winding system is also used here.
In the lab
For a movement of this tiny size, pretty amazing!"
|dial up||+-0 s/d||257°||0.2ms|
|dial down||+1 s/d||279°||0.0ms|
|crown right (12 up)||-2 s/d||251°||0.6ms|
|crown up (3 up)||-17 s/d||241°||0.1ms|
|crown left (6 up)||-15 s/d||229°||0.0ms|
|crown down (9 up)||-7 s/d||231°||0.4ms|
|Caliber base:||Bifora 52|
|Size:||5 1/2 x 6 3/4''' (measured: 13,0 x 15,0mm)|
|Number of jewels:||17|
monometallic anular balance (two legs)|
|Balance bearing / direction hairspring:||Counterclockwise|
|Adjust mechanism:||Short regulator arm|
|Construction type:||solid construction|
|Winding mechanism:||yoke winding system|
|Setting lever spring:||4 hole(s)|
Flume: K3 77|