These are very good delays and they are not rare. Prices swing wildly and I have observed that buyers will pay a high price for an AD-9 that is pretty beat up (working of course). I am certain there are different electronics associated with the 1980s versions. Anyone is free to elaborate. Here is good forum discussion on Harmony-Central. Some early versions are advertised as having a “rare black” label and the MN3205 chip. All of the price listings here reflect original AD-9s made in Japan in the 1980s.