Era
Quartz and resin arrive in force. Casio launched the G-Shock in 1983 and the F-91W in 1989, and the screw-back DW-5600C square and the A159 sit here too. Seiko's 7A28 quartz chronograph came out in 1983, and the slimmer 6309-7290 and the date-only 7002 carried Seiko's mechanical divers through the decade.
6 references we cover.

Seiko · Vintage Diver
Diveref 6309-7290
$410–$800 typical ask
32 on eBay

Seiko · Vintage Diver
Diveref 7002-700A
$360–$440 typical ask
16 on eBay

Seiko · Speedmaster Sports 100 (Giugiaro)
Chronographref 7A28-7000
$1,475–$1,725 typical ask
10 on eBay

Casio · G-Shock Square
G-Shockref DW-5600C-1V
$360–$950 typical ask
74 on eBay

Casio · Casio Classic Digital
Digitalref F-91W-1
$20–$130 typical ask
150 on eBay

Casio · Casio Classic Digital
Digitalref A159W
$50–$100 typical ask
201 on eBay