Vintage Omega in my collection, looking for more information

Hi everyone,

first of all, thank you to the founders of this forum, the amount of knowledge available here is unbelievable!

I have a small collection of relatively inexpensive watches and I am attracted by watches with a story. A few years ago I started looking into Vintage Omega and my girlfriend bought for my birthday a vintage Omega. Now, the relationship with that girlfriend finished but I still have the watch and now I would like to understand better what do I have in my collection.
From initial research, it looks like I have an Omega Seamaster Deville 1960 KO14750 (found on the website of vintage Omega watches). However, there are a few things that do not match.
1. the diameter of my watch is 30 mm (that is one of the reasons why I wear this watch rarely, it is too small for my wrist) and on the Vintage omega watches website, the watch with the movement 600 is 34mm diameter. Perhaps I got confused and the number 600 is not the movement?

2. there is no logo of Seamaster on the dial neither De Ville

Today I decided to open the case of the watch to look into and find out more information. Below is what I got:
Omega watch Co swiss
21487420 Omega 1 600
adjusted two (2) positions
seventeen 17 jewels

On the back of the case cover
Omega watch co
fab. suisse
swiss made
acier inoxydable
131.018
followed by a circle and a triangle

I have attached the pictures I took and I would really appreciate if someone on this forum could help me to find out the model, year and some reference on my watch.

Thank you for your help and I look forward to catching up.

Best,
gio_potter

Hey Ahsposo,

Thank you for the links, really appreciated! Not sure whether the movement has been upgraded, why exactly do you think that could be an option?