I really enjoyed your detailed review. I stumbled upon it in midst of a Google-search for Grand Seiko tang buckle; one of my best side-tracks, ever. 
Your photos are splendid. The SBGW001 should be the benchmark for clarity of design.
Lacking your patience in dealing with the fully-wound conundrum
, I opted for the less-concise PR version.
Just for fun, here's a pic of my SBGL017...
Thanks again for a terrific presentation.