The 16550 lasted about five years and changed the Explorer II completely. The caliber 3085 let the hour hand jump independently for the first time, which turned a day-night indicator into a genuine dual-time watch, sapphire replaced acrylic, the case grew to 40 mm, and the white Polar dial arrived alongside the black. It is the same movement generation as the GMT-Master II Fat Lady of the same years, and the two references share that jumping-hour architecture.
Its fame rests on a manufacturing defect. The white dials used a paint that discoloured, and examples that started stark white aged to a warm cream or ivory. Rolex corrected the fault; the watches it affected became the most sought variant of the reference, and a defect that would have been a warranty complaint at the time is now the premium. Sources split on whether production started in 1984 or 1985, and dated examples exist from 1984.
A short-run transitional whose most valuable feature is a paint failure. Cream tone and evenness do the pricing, which makes photographs under honest light essential.
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.