I've gotten a few emails of people looking for this seat specifically made for the Mini-Crab. The seat shown here is owned by Steven Mahoney #157, from the Seattle area. If anyone has a extra seat floating around and you no longer need it, let me know and we could help find it a new home.
These seats are extremely rare. This one pictured is in it's original condition. There are a few posts on this site with the Mini-Crab seat pictured.
There's even a great shot of the inventor of the Mini-Crab, William Sargent, sitting high on the seat for a Colortran print ad that appeared in an issue of American Cinematographer.