Good buy for £1400?
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Should I ask to see the movement?

 

Looks nothing like the others I have seen recently which are from known and trusted sellers.
There is a very nice one for sale right now in the private sales section here.

 

I'd also appreciate an answer on this, I've found another one with the same configuration:
Also comes with an extract, serial starts 26661

 

These certainly seem to be legit based on the other listings I can find for them: https://www.allvintagewatches.com/vintage-watches/omega-seamaster-30-paf-1968/

 

I can't really comment on the price, I've seen a few listed around £1,400 to £3,000 mark.