The midsize Bifora cal. 91 was used a lot in the 60ies and 70ies. It was vailable in two versions, one with fully integrated, indirectly driven center second and the other with a decentral small subsecond. Both versions use the same plates.
Like many Bifora movements, this one uses a Bishock shock protection system. It can only be found in Bifora movements.
On the dial side, there’s a yoke winding system.
|Number of jewels:||17|
Nickel anular balance|
|Balance bearing / direction hairspring:||Clockwise|
|Adjust mechanism:||Hairspring key|
|Winding mechanism:||yoke winding system|
|Setting lever spring:||3 hole(s)|
|Production period:||1962 - 1980|
Flume: K3 18|
|Mentioning in literature (years):||1962 - 1969|