Can anyone help re replacement mainspring for Cal 6139B (17J) as originals seem unobtainable. Seiko part no 401616, barrel+arbor assy 205613, arbor 213612. The barrel/arbor have same Seiko no for Cal 6106A (base cal for 6139B) as well as 6106B (also 6139A) but the mainspring is 401615 (which I can source). How does the 401616 differ from the 401615 as they appear to fit into the same barrel/arbor assy? I have measured the old spring (401616) (the slipping attachment has broken off) and dimensions are as follows (all mm, height 1.01, thickness 0.10, length 43.5 (could be +- 1.0), barrel diam 10.95 (say 11.0), barrel inside depth to top 1.24, cap thickness 0.23 and therefore spring space height calculated at 1.01 (similar to spring height). The slipping attachment has height 1.00, thickness 0.20 (thicker than mainspring) and 30 long joined to spring approx 6.5 from end of spring and slipping attachment. Any help/ideas will be much appreciated so I can fininsh my Pogue project.