5513 Mark II - Could this be the one?

[fizz]

So another day, another seller brandishing what they claim is an exemplary specimen. The seller is from HK, and highly reputed here. The price seems fair to me and I think it's a really lovely piece. There are some additional pics I've requested of the case back and movement which should come through in a day or two, but in the meanwhile, any comments on this? Warning signs? Anything that sends alarms bells ringing? Crown guards etc. ok?

Some key things to note: 5.9 serial no, from 78/79, original bezel claimed, original dial and parts within.

Appreciate all the help I can get.