I just bought this supercool PC3. I had one back in the day, was my first IBM compatible pc. Mine did not have the 3.5" vertical drive, just the one 5.25" floppy with the internal 30MB harddisk.
I actually never saw these machines with a vertical 3.5" drive installed, i assumed it was aftermarket, or done by the previous owner, but... the seal on the case is actually still intact, so it was never opened, and the cut in the front for the drive is perfect, not done afterwards, so i assume this was a factory option... btw showed this thing on the facebook page as well.
Later on i found these pictures on ataripc.net showing another machine with vertical 3.5" drive: http://www.ataripc.net/pc4-286/atari-pc4-photo-gallery/
I will clean it up and possibly whiten it, in time i would like to add a bootable ISA SD card or something. Will look into that.
Came with a PCM124 moitor and Atari keyboard (ZXCV keys are not working, have to check it), mouse is missing. Was not eaten by the cats. Checked it.