Longines introduced the calibre 12.68Z in 1938. The basic sub second variant is found in Longines watches up until the calibre was phased out in 1959/60. The 27mm movement was ideal for modification and some variants where made. The modifications where given an additional letter to set them apart, the exception being a mono pusher stop second variant. The pointer date is known as a 12.68ZQ. The centre second variant as a 12.68ZS. These movements have varying levels of decoration, according to when they where made and what market they where sold to. The 12.68Z balance also evolved from non-shock protected to fully shock protected during it’s long production run.
Longines Calibre: 12.68Z-ZS-ZQ
- Made approximately: 1938-1960
- Made in Switzerland
- Power reserve 41h
- 17 Jewels
- 18000 B/A
- Lift angle 44°
- DM 27mm
- H 4.25mm-5.7mm(ZS)
Surface finish on the 12.68Z varies from fine gilt plating with no surface decoration to fully decorated rhodium plating with gilt lettering. All the screws are highly polished and well made. The bridges have chamfered edges and a nice cut design. Ratchet and crown wheels have a fine finish. Standard jewel count.
Surface finish on top side of the plate and bridges: 7-8* Points
Surface finish on screws: 9 Points
Surface finish on crown and ratchet wheel: 8 Points
Movement Jeweling: 7 points
The movement was a standard design for 1938
Movement design innovation (for 1938): 6 points
The Longines base plate varies from no decorated to perlage or cote de geneve. Winding mechanism is very solid with no wire springs. Gear train has a nice finish on wheels and pivots.
Base plate finish: 6-7 Points
Setting and winding mechanism: 8 Points
Gear-train finish: 8 Points
Movement durability: 7 Points
First model did not have shock protection. A early version came about 1940, but soon replaced with inca shock.
2-3* Bonus points
No wire springs where used while making the 12.68 series. That makes for fantastic workmanship.
3 Bonus points
The 12.68 ZS modifications are very well made manufacturing a complete bridge rather than a add on.
5* Bonus points
The 12.68 ZQ date complication is very well made with a quick set application
Date Change snapines: 6 + 4 points for a quick set lever.
10* points total
I will add details of the 12.68Z mono pusher at a later date.
The Longines calibre 12.68 in good condition gives excellent accuracy.
Accuracy: 9 points
Power reserve is fair: 7 points
Longines calibre 12.68Z-ZS-ZQ summary:
Surface finish on bridges and top side of base plate: 7/8*
Surface finish screws: 9
Surface finish on ratchet and ratchet wheel: 8
Movement Jeweling: 7
Movement innovative design for ca 1938: 6
Base plate finish: 6-7*
Setting and winding mechanism: 8
Gear-train finish: 8
Movement durability: 7
Total bonus points: 3-13*
Accuracy: 9
Power reserve: 7
Grand total: 85-97*
*Surface finish and variant.
Weakness: barrel arbour surface in barrel bridge gets worn. A sign of this is when you see wear marks of the ratchet wheel in the barrel bridge surface. Re bushing of barrel bridge solves the problem.