The Constellation range appeared at Omega in 1952. The movements are certified chronometers and the case backs are engraved with the image of the Geneva Observatory as well as eight stars.
The shape of the case is called "C Shape" on this reference, a variant of the cushion case. A brushed bezel and chamfers are also part of it and give a beautiful play of light to the whole.
You can follow the review of an Omega of the same reference in this blog post:
Movement: Omega 564 self-winding chronometer 24 jewels - quick date setting (to the last notch)
Bracelet: Omega 1040 "Bricks" 19 mm endlinks 518 for a wrist with a maximum circumference of 17.5 cm
Condition: Superb condition, this watch has never been polished. The acrylic glass has been replaced with a generic glass. Very good condition for its age.The movement has been checked and regulated, this Omega works perfectly.
