It does vaguely resemble the beige G3 in terms of overall shape and size, but many of the details seem to have more in common with a similar-era PC case I have (with the sideways-mounted PSU and shorter-wider shape). That stamped-in Apple logo does suggest that it's genuine, though. The motherboard tray does strike me as similar to the production G3 as well, if I remember correctly.
As for the extra slots, well, maybe this was an early prototype case originally intended to be more in line with the 9500/9600 (and perhaps it was developed into it at one point), and they simply cut it down to size at a later stage to get the G3 (which, aside from # of slots (and probably height; I've never seen a 9x00 in person closely enough to make detailed observations), is very similar to the 9x00, I think). It's purely speculation at this point, I think.
Who knows, you could have a veritable gold mine there!
I'm eager to hear (and see) more!
c
As for the extra slots, well, maybe this was an early prototype case originally intended to be more in line with the 9500/9600 (and perhaps it was developed into it at one point), and they simply cut it down to size at a later stage to get the G3 (which, aside from # of slots (and probably height; I've never seen a 9x00 in person closely enough to make detailed observations), is very similar to the 9x00, I think). It's purely speculation at this point, I think.
Who knows, you could have a veritable gold mine there!
I'm eager to hear (and see) more!
c