Help needed on model identification

Hello and Merry Christmas!!

This Omega was recently found in my late Grandfather's house. My Father doesn't know too much about the watch apart from what is obvious in the pictures. As you can see there is no reference to the model on the watch face itself. From the little research I have done myself I found a UK Omega catalogue from 1972, which is the date of purchase, and there is an Omega Constellation with the same Case Ref as written in the purchaser booklet: BA1675436. However as you can see the watches bear little resemblance.
http://www.old-omegas.com/catuk72.html
http://www.old-omegas.com/pics/catuk72/p9.jpg

Any help on identifying the model or if anybody has anymore information on the watch, it would be very much appreciated!!

Thank you, TJ.

If the watch that the booklet came with could be found it looks as if it was a 14k white gold case with a 712 chronometer movement. Could be rather interesting.

Ah I see. There is obviously another watch to be found! Thank you!