Help to identify this Seamaster

Hi guys, I have an Omega Seamaster as shown in the picture, which was given to me by my grandfather and he said when he bought it circa 1983 (this was said by him but now he's nearly 90 years old already so I'm not sure if that is a truth or not). Can you help me confirm that this watch is a replica? Is it official Omega or is it a fake, and if it is a genuine watch, what series does it have?
The things I know about this watch on the front are:
- Omega Seamaster CO-AXIAL CHRONOMETER 150m/500ft and a little Swiss Made at the bottom
- There is no number to display the time, only a date display place located at 3 o'clock
-Looking at it, it looks like the hands and the places showing the time are black, but looking at it slightly tilted, it is quite beautiful turquoise blue, the clock hands have a small part with reflective when entering the dark, the hour markers also have a point similar small reflective
As for the back side:
-On the watch's case near the strap there is an engraved number 604 and it looks like a laser printed number 06 or 90, but I think it's 06
-On the back edge of the glass read in a circle, there are words like OMEGA06 Seamaster Aqua Terra Co-AxialEscapment 150m/500ft
-the part of the machine inside the glass, I can't find the serial number (I read on the internet that I have to take it off to see, is this really necessary?) and the part of the machine says OMEGA embossed with the symbol, under the word omega it says TWENTY-FIVE 25 JEWELS SWISS MADE and it does have some pink jewels inside

Here's what I have about my watch, thanks for reading, hope you guys have some clue about it.

I’m happy to have a forum guru correct me but I thought the aqua terra line first started in the early 2000’s and was fitted with a co-axial. Not from the 1980’s

Thanks for reply, 1980s was said by my grandfather, I don't know if the watch was bought that time or not cause he's now nearly 90 years old, sorry for not telling this part, but do you have any clues about this watch? I was trying to search for nearly 2 days but I didn't know the series so everything went to an end quickly

Based on this website article https://zealande.com/blogs/we-talk-about-watch-models/omega-aqua-terra
I’d say you have a genuine fake. this specimen looks like it was made to be a first generation but that didn’t come out with a bracelet. Leather only in 36mm or 42mm.

another thing is every AT I have seen has had some kind of dial detail in the way of lines, vertical or horizontal depending on model.

I’ll let the experts tell you what is what and correct anything I got wrong but it doesn’t look legit from where I’m standing. Happy to be proven wrong.

😁😁 Thanks for letting me know that, I feel better know why I couldn’t find any clues about it haha

I am sorry that you spent so many time to write your post but the watch it's a grosolan fake. Only one pictures with the mechanism was enough to see that. Regards.

Sadly to know that, but it’s worth to have a try to identify my grandfather’s treasure, thanks for your confirmation😉

Thank you, I’ve tried the best to make sure there will be no confusion in identifying it, everyone’s time is priceless and I’m being helped on a free case, thanks for letting me know it’s fake one, sad but it’s worth it😉