[G6Tanuki]

I'm wondering if they could be something to do with entertainment equipment like pinball-machines or one-armed-bandits? They were often _very_ well-engineered [to survive abuse by punters who were apt to kick/rock/punch the machines when they lost] and had loads of access-denying seals/covers on them to prevent illicit tampering (either by punters or by the supervisors of the arcades, who were not averse to tweaking things to reduce payouts, then pocketing the difference at the end of their shift).