I/O アイ・オー 1982年3月号 : 工学社 : Free Download, Borrow, and Streaming : Internet Archive

I/O is an old computer magazine

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The mag seems ridiculous, mostly ads, then a lot of circuit work, then type-ins which are mostly ASM in giant 16x16 grids with checksums. And prices were insane, VIC-20 for 54,800¥?! That's like 4x the US price (<$200).
@mdhughes I'm more interested in that multicart expansion chassis behind the VIC. That's completely different from the VIC-1020 chassis sold in North America. It looks like it's made from the same mould as the VIC case. I wonder if it was just a prototype or actually made it to production.

@mnemonicoverload Looks like the standard VIC-1010:
http://www.sleepingelephant.com/denial/wiki/index.php?title=VIC-1010_Slot_Expander

Tho I'm of course an Atari boy, so dunno how popular that was here; the listed price of ¥29,800 also seems excessive; that's still more than the base cheap-ass computer cost in the US!

VIC-1010 Slot Expander - DenialWIKI