Seiko 6309-729A/729B "Slim Turtle" was in production approximately from 1982 to 1988, a run of approximately 6 years, carrying the 6309 automatic caliber in a 43 mm case rated to 150 meters.
The slim-case export variant; crowd-sourced caseback data extends some production as late as 1992, and the orange -729B is the rare one.
Dates carry a "c." because that is what honesty requires: Seiko's own archive gives only approximate production windows by caliber, so the file states the documented range and marks it as such rather than inventing precision.
The full collector's file for this reference — variants, dial codes, and the authentication walk-through — is on the writing schedule; the specifications above are the permanent record.
Vintage Seiko divers are the most frankenwatched category in the affordable vintage market. Aftermarket dials, bezel inserts, hands and crowns outnumber originals in the wild, and correct-looking watches are routinely assembled from parts. Before bidding on any reference in this family: ask for caseback and movement photos, check that the serial's production window matches the dial code, and price a full service into every purchase.
Production windows and specifications compiled from documented collector references and period catalogs, cross-checked across independent sources; manufacturer records for this era are approximate by Seiko's own account.