Once again, thank you very much for all the inputs received from this forum.
I wish to conclude this thread by sharing the other two vintage Omega pieces that my late parent bequeathed. Watches have no cross hair but have minute markers which piqued my interest on the other watch that eventually led me to begin this thread.
These other watches are the Omega Seamaster Calendar Cal 503 in cream dial and an Omega Seamaster Cal 565 in silver dial. Pictures in wrist shot are posted below. Both watches are still functioning after 61 years and 49 years respectively. I am awed at the simple collection of my parent, something that I will pass on to the next generation. Again, many thanks!