The 214270 took the Explorer to 39 mm for the first time, on the caliber 3132 with a Parachrom hairspring and Paraflex shock protection, and it split into two clearly different generations during its own run. Early examples, the Mk1, carried hour and minute hands sized for the previous 36 mm case and unfilled 3, 6 and 9 numerals, which drew immediate criticism that the hands looked short against the wider dial. Rolex lengthened the hands and filled the numerals with luminous material on the Mk2 a few years in.
Both generations wear the same reference number, and both are legitimately a 214270. The market prices them differently and buyers looking at photographs frequently cannot tell which one a listing shows.
One reference, two watches. The hand length and the numerals are the entire distinction and they are visible in any decent photograph, which makes this an easy check that is often skipped.
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.