Looking at this vintage listing, seller states personal watchmaker has recently completed a service and it is running +10s/day, but that the top chrono pusher does sometimes stick. This sounds like a common 6139 problem related to the gasket. Is that expensive to fix?

Should I be concerned about anything in these photos?

 

I'd be concerned that any watchmaker that supposedly did a "service" didn't bother to clean the case, which is clearly filthy, as well, which likely means they didn't bother to remove the pushers and clean the gunk out of them.

I'd pass on that alone even if it was actually serviced.

 

This.

The other thing is that the culprit can be the chrono mechanism, so don’t count on it being only the pusher. I have a 6139 that I bought for parts, and it has the same issue, even with the movement out of the case, meaning it clearly needs a service.

 

Thank you both for your guidance. Great points. It's still tempting to take a chance on...
I'll press them for a bit more info but perhaps best to hold onto my dollary-doos this time.

$500 seemed like a good price given the appearance of the rest of the watch, but I'll admit, I hadn't been looking into this line prior to coming across this piece this morning so I don't have a good barometer for price beyond what I can dig up in the usual aggregators.

 

Out of interest, what does the rest of the watch look like?

 

Hesitated to draw attention to its listing by posting the particular reference, but if that happens, so be it. It is posted elsewhere, so others are seeing it.

Got a response about the condition, photos were from before the service, and they don't want to open in case they might harm the gasket. About the pusher, their watchmaker said that the movement is fine, but the spring of the watch is kinda old so sometimes it is too weak to bounce back, but they are trying to source a replacement part.
I have asked if they can provide a new photo or video of it including the back. Should be easy to see if some of the spots nearer the bracelet have indeed been cleaned.

 

Awaiting a video from the seller. That should clear things up a bit.

 

Umm... How does one harm a gasket when opening a caseback? That sounds shady. Also, couldn't the watchmaker have supplied them with a picture of the movement? My watchmaker offers a 1 year guarantee unless the caseback is open, so maybe that is what the seller meant
I'm telling you to pass on this. I have no knowledge about parts availability where you live but I live in a 3rd world country and sourcing replacement parts for these is not that hard and almost all reputable watchmakers accept to work on these watches.
Also, does the seller have proof of service? My watchmaker is not that keen on taking pictures since he's very busy but he always provides a receipt detailing the condition of the watch and what was done to it.