I was just going to ask about that. I've never used any Sun keyboards. They look quite cool, especially the unique speckly "granite" versions like this one:
I understand the Type 1 through 3 boards were mechanical, and thus preferable to the subsequent Type 45 (RD) boards. A lot harder to find, tooI don't think I've ever seen anything earlier than a Type 4 on eBay.
Are the RDs particularly well made, or have other interesting features? I'm sure some Sun experts are lurking here... Maybe one of them could wade in and elucidate us.