Longines 17.25, 18.25, 19.25 (17-19'''), Balance staff, Ronda: 912
- Manufacturer Ronda no: 912
- Total length: 445
- Fits cal: 17''' 17.25, 17.27, 17.79, 17.89
- Fits cal: 18''' 18.25, 18.79, 18.80, 18.89, 18.90
- Fits cal: 19''' 19.25, 19.26, 19.79, 19.80Z, 19.80ZZ
- A: = 445 (ronda A).
- B: = 218 (ronda B).
- F: = 80 (ronda K).
- G: = 130 (ronda J).
- H: = 56 (ronda G).
Conversion: Ronda to DCN
- A = A
- B = B
- J = G
- G = J
- K = F