Thanks, it says the Z80 runs at 4.1MHz which makes the strange /7 frequency divider plausible.
30KB RAM total (15 SRAM chips of 2KB each)
Is this video yours?
You can indeed see the 15 SRAM chips, the chip next to the Z80 is probably the BIOS ROM. The 3 QFP are mentioned in the manual as "ATC"(?), I/O, and VRAM controller.