The 6350 is where the name lands. Earlier Oyster Perpetuals had been carried up mountains and worn on the 1953 Everest expedition, but this is the first reference with Explorer printed on the dial, and the first with the Officially Certified Chronometer text that separated it from the Precision-marked 6150 sharing the same A296 movement and the same 36 mm case. The two references ran alongside each other in 1953, which is why the question of which one is the first real Explorer has never fully settled. The file records both and takes no side.
One variant does most of the work in the market. A minority of 6350s left the factory with a textured honeycomb dial, also called waffle, and it appears on no other Explorer reference before or since. Pencil hands turn up in place of Mercedes on some examples. Sixty years of service have thinned the survivors further: gilt dials refinish badly, and a refinished 6350 is a different watch commercially from an original one.
The founding reference of the line, with a dial variant that carries a large premium and an equally large forgery incentive. Originality of the dial is effectively the whole 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.