Era
Casio's first Frogman dive watch arrived in 1993 and Seiko's SKX007 in 1996. This is also where we file the DW-5600E and DW-6900 G-Shocks and Casio's A168.
8 references we cover.

Seiko · SKX Diver
Diveref SKX007
$370–$625 typical ask
124 on eBay

Seiko · SKX Diver
Diveref SKX009
$390–$525 typical ask
153 on eBay

Seiko · SKX Diver
Diveref SKX013
$470–$1,100 typical ask
26 on eBay

Seiko · SKX Diver
Diveref SKX173
$300–$480 typical ask
10 on eBay

Casio · G-Shock Square
G-Shockref DW-5600E-1V
$110–$160 typical ask
163 on eBay

Casio · G-Shock Round
G-Shockref DW-6900-1V
$100–$230 typical ask
185 on eBay

Casio · G-Shock Frogman
G-Shockref DW-6300
$230–$650 typical ask
108 on eBay

Casio · Casio Classic Digital
Digitalref A168WA-1
$65–$150 typical ask
181 on eBay