Looking for obscure Sonic artwork

[Osmium]

Hello, it's been a while since I posted here. I'm trying to look for some very old and obscure Sonic artwork. I've talked about it before, the detailed backgrounds seen in these images. http://sonicjam.wikidot.com/sisghzs:other-sonicscenes

For years all I've seen is these versions heavily blocked by text and renders of Sonic, but this all changed when I saw a twitter post that made my jaw drop. 

You can see one of the background images is partly revealed, showing several characters I've never seen before. Apparently this exists in some Japanese calendar from 1992 and I wonder if the other images are in here as well, along with more that have no presence online whatsoever. I want to find the source of these images as they've been elusive to every single search I've ever made. If some of you have ties to others or especially good searching skills I implore you to ask everyone you can if they know anything about these images and/or this calendar which exists out there somewhere. 

I'd appreciate it also if someone posted this question on Sonic Retro as well. I would myself but I'm only a pending member. Let's try and unearth these drawings which have been hiding for roughly 30 years.