Help with vintage Omega Seamaster De Ville 165.020

Hi all,

Just wanted some help with regards to the authenticity of this Omega Seamaster De Ville I purchased. Please refer to photos attached. The serial number on the movement shows the watch is made in 1968, however, as I understand, the Omega Seamaster De Ville was only made till 1967? Is this right?

The movement is calibre 552, I believe the rotor was removed for the photo.

Omega Seamaster De Ville
Gold and steel case
Automatic
Calibre 552
Ref 165.020

Thanks.