The Scubapro 450 is based on Seikos 6306-7001 model, and were produced in the late 1970’s as part of a marketing contract in conjunction with the Scuba-pro dive equipment company. The model it’s based on is a Japanese domestic market watch produced alongside the very similar 6309-7040. The difference between the calibre 6306 and 6309 is the 6306 has a kanji day wheel, has four extra jewels, it has a hacking mechanism and has different machining around the crown making the opening slightly larger. The difference between the Scubapro 450 and a stock 6306 is just the printing on the dial. The most obvious difference is the “Scubapro 450” script situated above the “Water 150 Resist” on the dial, but a harder to see change is the dial code went from 700L T to 700J T. It’s generally accepted that the Scubapro versions were produced between 1978 and 1979 but to muddy the waters examples have surfaced with caseback dates of 1976, 77, and 83. Were these actually produced in those years or have the casebacks been changed? The 1983 example is doubly strange because that one post dates 6306’s end of production date of 1981! As ever with vintage Seiko nothing is clear cut – part of the appeal maybe? The example featured below is in outstanding condition and belongs to a very knowledgeable UK collector. It came in for a full movement service so I seized the chance to document it!