Yes, that looks original. There were two types of quartz movement in these watches a cal 1441 and cal 1438. This configuration (caseback, crown and mercedes hands) you show was the earliest (1988-89) and should have the cal 1441, a very accurate movement that Omega only used for a year or so.
The trouble is that many of those movements were swapped out in services either for the 1438 or an ETA equivalent. The only way to know is to look.
The price seems extremely reasonable so worth checking everything is functional.
I agree it looks good, especially for that price. But I would want to see the movement and make sure there wasn’t leakage from a battery - a lot of people put watches away when the battery dies, it leaks, and the movement is ruined.
The bezel is 18k gold and solid and the crown is gold plated. I have seen examples where the crown has peeled but this one appears to be good.
Padders is right that the hand and crown changes did not exactly coincide with the movement change, however this particular caseback was only found on the very earliest incarnation (actually 1987-88) and will have almost certainly had the 1441. When there are examples with the 1438 it will be because it was swapped out.
