It is rumored that Honda motor company in the 60's had far too many engineeers; the s600 cars were famous for desgin changes, often where the change did not necessarlity respresent an improvement or a real change in functionality. When restoring an sCar, this presents a problem, especially if you are trying to match the factory original as closely as possible. Parts are already rare, and now you have to find amongst those rare parts, the correct version of part to match the serial number of your car!
Take for example the clutch slave cyliners. There were four distinct models used. (Thanks to Don Laughton for some very detailed information)
AS280 4581 or as latter numbered 22700-504-003 was used for all S500s and S600s to Engine number E1002296. It is the rear feed, rear, horizontal, rear bleed slave cylinder. By the engine number, it may not have been used on more than 25 export cars.
22700-504-013 was used on 600s from 2296 to E1002490. This is a rear feed, top bleed design.
22700-504-023 was introduced at 2491 and was used on the rest of 600 production and for the first 600 or so chain drive S800s. It appears to be identical to the "504-013". However, there was also a change in the piston, piston cup and circlip... This was due to a change in bore diameter. To confuse the restorer even more there is also a change in the external rubber boot, because of the change in bore diameter.
22700-504-033 was used on the last chain drive 800s and all the live axle 800s. These are the cars with the stamped steel, pivot ball, release bearing fork. It has a vertical feed and off horizontal angular bleed.
After months of searching, and just when you think you have found the right rare part for your sCar, double check the parts manuals, you may not have the right part after all. Remember you are a slave to the clutches of the Honda Engineers. At least in the case of the clutch slave cylinder, you are lucky, the changes were only for the amusement of the engineering staff, the complete assemblies are all interchangable, but not necessarily correct the numbers