There are quite a few 59 calibre watches in circulation, so routine service should not be a major issue if the main parts are in decent condition. If this is not known, I would be wary. The price seems a bit high, as one that is in good shape with a serviced movement would be in the $1000-1500 range. The dial on the watch you are looking at seems pretty good but I suspect the hands may have been swapped at some point. The the shape looks a little odd for the style and both the second and minute hands, go slightly past the second track. Compare the one you are looking at to the photo of Smurfdivers. A generic replacement crystal can probably be sourced in the vintage NOS or aftermarket parts supplies.
Here is a link to a Solar Aqua on Derek Diers website for comparison, although neither is the same model you are looking at. The 30-31mm is often called boys size, so unless you have tried one one, people are often disappointed with these cases. I had a Solar brand watch fron the 1950's that I gave my daugher and she loves it. If I had kept it, I would have it on a bundt strap, which wears a tad bigger.
https://watchestobuy.com/shop/solar-aqua-watch/Click to expand...