Patent might be the wrong word.
I just mean it seems almost identical in structure to an extended 2.
Some nitpicky comments about design similarity (although you probably already know this):
The Apple Extended II had a single-row return key (next to the quotes key), and a full-size delete key. the "|" & "\" key was on the QWERTY row, above the return key, and was somewhat longer than a standard single-width key. The L-shaped return key was common among third-party Mac keyboards (and perhaps required, to hedge against design-copyright infringement claims? I don't know).
Also, the Apple Extended II had flatter keys with less contour. Although as I understand it, two significant variants of the Extended II were made, and there might have been differences in the key shape. To me, the profile of the keys with this board is reminiscent of the not-as-classic Apple Design keyboard (which was not-as-classic only because of the lack of quality switches, not because of the key design).
Without counting, I'm confident that the PowerUser 105 and the original Apple boards have the same number of keys. There is only the size/rearrangement difference in the area of the return/delete/"pipe and backslash" keys.
I love that this has white Alps, that makes it a great find. I think it's terrific that these older, unknown, quality keyboards are being discovered and pulled into service. It feels like we're techno-archaeologists in a way, finding sophisticated alien artifacts buried in the sand, and supplanting our own clunky inventions with them.
