As you can see here on an original Omega service blueprint the mainplate was printed 1438 from factory so your movement is maybe an later replacement with the Omega specific parts swapped. https://www.oldswisswatches.com/wat...-calibre-movement-and-spare-parts/omega-1438/
Thats not a big deal because technically the 1438 and ETA are the same.
Thanks for the info Sirtaifu, it’s a shame I can’t identify the watch from the movement, from the picture does the movement look genuine ? The ones with Mercedes hands seem either to have the 1441 or the 1438
Sorry to be a pain, but does anyone have any more info on the Italian made cases ? thanks