ask a watchmaker to remove the back of the case. Then you can take pictures (or at least read the information) on the movement and inside of the case back. What you want are:
1. the movement's serial number
2. the case's serial number
3. the case's ref. # (4 digits)
From just the picture you provided, I would guess that the watch has an automatic movement, cal. 1121. Cal. 1120 is the base movement and at that time was the thinnest automatic movement in the world (I think it is still the thinnest automatic movement with a full rotor). Cal. 1121 added the guichet date and with it, a very little bit added thickness.
We don't talk about current valuations of specific watches on this forum, so if anybody would like to provide specific information - please do so through PM. As always, Loungers usually recommend taking the watch to one of the large auction houses for valuation, i.e. Antiquorum, Christie's, Sotheby's.
Best Regards, Dan