I want to know the authenticity of this quartz watch, it belonged to my grandfather

Hello people, I write this post because I have a "problem". I got this watch through my grandfather. My mom and my grandmother bought it as a present from a jeweler of the family, a well known man in my town who always made custom jewels to my family and I believe he already passed away.

We are not sure but my mom says it was bought in 1989. It was in the store side by side with a similar one, squared case, but the jeweler said this was more iconic. The more I know about watches I am not so sure about how iconic this is.

I have checked the Omega web with no results. Then I checked the Omega reddit, where somebody pointed me it might be fake as the logo in the back of the case is supposed to be inside the case and not outside. Then I reach out to you. The information in the back of the case says "18k 0750 QUARTZ".

I am positive about the quality and authenticity of the gold. This led me to think, why would someone fake a case of a quartz watch and strap it in 18k gold? I don't have the tools to open it and it is impossible to me with the COVID scenario. I am not planning to sell it, I just want to know more about this.

Any information about this would be appreciated. As you can see it was very worn, so I guess it made my granpa happy afterall.

I think this watch is fake or something I haven't seen before.

No "SWISS MADE" on the dial?

Spain

That posibility makes total sense to me, I mean my grandmother didn't know anything about watches but she was extra careful with gold and very picky with the jeweler. I might end up selling the gold and buying a watch myself.

Disagree. Not unusual for that era. Sure, need to see more, but it's not obviously wrong.

Tom