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· Explorer II
Explorer II Reference 16550
"Rail Dial"
A significant modernisation of the Explorer II: out went the dramatic orange arrow hand (replaced by a more refined red-tipped 24-hour hand), in came sapphire crystal and the new Cal. 3085 with quickset date and independently adjustable 24-hour hand. The white dial variant is particularly sought, especially the rare "creamy" dials that have aged to an off-white. A short-lived reference — only four years — making it rarer than both the 1655 and the 16570 it preceded.
Notable: Rare four-year production window. White dial versions with patina are among the most collectible Explorer II references.
Technical Specification
| Reference | 16550 |
| Production years | 1985–1989 |
| Case diameter | 40 mm |
| Case material | Oyster steel |
| Movement | Cal. 3085 |
| Jewels | 27 |
| Frequency | 28,800 bph |
| Power reserve | 50h |
| Crystal | Sapphire, flat |
| Water resistance | 100m |
| Bracelet | Oyster 78790 with Oysterclasp |
| Lume | Tritium |
| Dial colour | White or black |
| Numerals | 3–6–9–12 Arabic plus 24-hour bezel |
| Hands | Thinner red 24-hour hand (replaced orange arrow), Mercedes hour, baton minute |
| Crown | Triplock Oyster screwed crown |
| Date | Yes — date at 3 o'clock with Cyclops |
| Bezel | Fixed stainless steel 24-hour bezel (narrower font) |
| Serial range | 9xxxxxx |
Variants & Production Marks
White "Polar" dial
Black dial
Rare "cream" aged white dials