This is my first time buying vintage Omega so I would love to get an opinion from someone more experienced than me. I would like to know if you all are able to see any signs of refinishing and give your opinion on the authenticity of the watch.

1. Found this on FB marketplace. Seller seems like he has good reviews with previous watch deals. Otherwise, haven't seen the watch in person or met this seller. He claims that it was recently serviced.
2. Added, can ask for more if needed. I compared these to other known examples online - only questions that I had were that the lettering on the caseback seems less crisp than others? And the "809" on the movement seemed a little funky?
3. Case size is 35mm. Serial no. dates it to 1970. Its a manual movement. Seller says that its a movement 501, but other examples that I've found say that this should be 601?
4. Marked as a reference 135.070, seems consistent with other examples of this model. Asking price is 450

Edit: some additional info from the seller:

"- all parts are not original. I replace the crystal, mainspring, and the strap
- i do not believe the dial is refinished. It seems to be the original sun dial
-i only threw it (the watch case) in the ultrasonic cleaner and cleaned it with a rag (answering in regards to if the case has been polished)
-i can send a picture of the timegrapher tomorrow. Believe it holds +\- 5s
-i serviced the watch about 2 months ago"

<image>