Watch type
Watches made for the water. Omega introduced the Seamaster 300 in 1957 as a watch for professional divers, and IWC added the Aquatimer in 1967. Longines' Super Compressor uses an EPSA case that presses its back harder against the gasket as the water gets deeper. Whatever the dial says, treat a vintage diver as not water resistant until it's been resealed and tested.
6 references we cover.

Omega · Seamaster 300
Diveref 165.024
$7,525–$12,675 typical ask
23 on eBay

Longines · Super Compressor diver
Diveref 7042
$10,250–$10,675 typical ask
4 on eBay

IWC Schaffhausen · Aquatimer
Diveref 812 / 812 AD / 1812
$10,200–$14,675 typical ask
2 on eBay

Tissot · PR 516
Diveref PR 516 (refs. 44544, 44622)
$260–$370 typical ask
52 on eBay

Tissot · Sideral
Diveref Sideral / Sideral S
$270–$525 typical ask
49 on eBay

Zenith · Defy
Diveref A3642
$1,675–$3,700 typical ask
25 on eBay