That is a messed about example of a very low value watch of little desirability. The case number may well be on the bracelet clasp. It often is on 80s Omegas with integrated bracelets, and this is from the first half of the 80s IMO. The movement serial is long gone along with the original movement. It was not a like for like replacement. Don't pursue it too hard, it is in essence junk worth maybe tens not hundreds of $/£/€