Brand
Louis Brandt started what became Omega in 1848 in La Chaux-de-Fonds, assembling pocket watches from parts made by local craftsmen. In 1894 his sons began selling watches under the Omega name, and by 1903 it was the name of the company. Around 1930 Omega joined Tissot in the SSIH group, and Lemania came aboard in 1932 as the chronograph specialist, which is why so many vintage Omega and Tissot chronographs share movements. The big names arrived after the war, with the Seamaster in 1948, the Constellation in 1952 and the Speedmaster in 1957. Used buyers mostly hunt the 1960s, from pie-pan Constellations and Seamaster 300 divers to the Speedmasters of the Moon years. Omega made a lot of watches, so you can afford to be picky about original dials and cases that haven't been polished flat.
6 references we cover.

Omega · Speedmaster
Chronographref 145.022
$4,975–$6,875 typical ask
202 on eBay

Omega · Speedmaster
Chronographref 105.012
$11,425–$19,100 typical ask
17 on eBay

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

Omega · Constellation
Dressref 168.005
$2,500–$3,275 typical ask
135 on eBay

Omega · Seamaster De Ville
Dressref 166.020
$1,025–$2,500 typical ask
127 on eBay

Omega · Genève
Dressref 135.070
$525–$975 typical ask
88 on eBay