Just picked this little beauty up. It's a ladies ST566.0034, caliber 552. Could it be called a ladies baby Flightmaster.
Nice! It's not a cal 552 and I'd say it's a 68x calibre which is very similar to the 550 series but at about 2/3 of the size. Great little design. Cheers, Chris
Zooming into the movement pic, I think it says 684. Excellent workhorse movement in the same vein as the 55x and 75x movements, I have one in my Seamaster 120. Update: the Omega vintage database says 681 so