Rolex 6610 was in production approximately from 1955 to 1959, a run of approximately 4 years, carrying the 1030 automatic caliber in a 36 mm case rated to 50 meters.
The transitional reference, thinner cased on the new 1030 - and disputed at both ends, with sources splitting on when it started and when it stopped.
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.
The Explorer's fraud pattern follows its production lengths. On the long references, especially the 1016, dial generation is the real identifier and the serial alone settles very little: gilt, matte and service dials each belong to specific windows, and mismatched combinations are the most common problem in the market. On the 6350 the honeycomb dial carries a premium large enough to attract forgery, so that claim needs independent opinion rather than a seller's description. On the Explorer II, the 16550's cream dial is graded by tone and evenness, which photographs distort easily, and the 1655's orange arrow hand is a frequently replaced part. The Rolex serial lookup on this site covers every reference in this family.
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.