Good to hear the seller took it back and the relationship was unspoilt.
I spent a few years working my way through 56GS models to find two keepers - sometimes you can only really learn the final details with it in your hands under under a loupe; no amount of website guides or hi def photos can tell you everything.
I would heavily recommend the Japan route, not just on price but generally the sellers highlight issues and take good photos. You can then compare to sites like Gerald's, mentioned above (grandseikoguy.com) and make a judgement. Note the import taxes though for your country.
One this example the black dial, text spacing/font and polishing were the main red flags, as noted, but also the operation of the day/date advancement at first stage can also be an fiddly and expensive fix if required at service. More difficult to check, and my watchmaker has a few stories of worn parts and bad 'temporary' fixes over the years.
Having the original facets and Tanaka lines I believe is imperative for these 'Grammar of Design' cases. Note how the original lugs brusing looks - always a good tell.
Here's one of my keepers, originally bought as a parts watch, obviously, for ~$250, but came with the XQB GS bracelet and turned out to be surprisingly clean inside. I am hardly ever interested in patina, but the 'Mouldy Lemon' has become a warm weather beater. Note the 56 dials are prone to discolouring and changing.
Good luck.
Click to expand...