authenticating omega speedmaster date omega 3513.50 - having a hard time

[abexpix]

looking to purchase online from someone who seems reasonable but doesn't have papers/box. Ay help would be appreciated -- been eying this watch and it seem to be a good price.

I tried to look up based on the serial number on the back, but it doesn't seem to check out. Also, is the 850 on the bracelet is a weird spot?

Front video:

https://imgur.com/a/CgK2ZHN

back:

https://imgur.com/a/35FAJJV

longer video:

https://imgur.com/a/XQ9TUWd

thanks!

 

[Archer]

Serial number: 90388105
Article ref: 35135000

Serial number matches the model...

 

[abexpix]

Archer

Serial number: 90388105
Article ref: 35135000

Serial number matches the model...

the location of the 850 threw me off - every other picture I have seen has it in the corner. what does this mean?

 

[Archer]

abexpix

the location of the 850 threw me off - every other picture I have seen has it in the corner. what does this mean?

Nothing - it's fine.