"Holmes 77" was a rules expansion for Holmes put together by Thorkhammer, IIRC. That is just someone's bootleg hardcopy of it.

The later "printings" of the rules supplements were really just glorified photocopies. I ordered Blackmoor in the late '80s and received one that looked like that. The cover was just thin white paper (the same stock as the rest of the booklet) and the cover art was darker than the original. They are mentioned on the Supplement page:

Note: black-and-white reprints of the Nov 79 editions were also later released, probably as stocks of that print ran out.  They are basically photocopies; some sources have reported paper-thin covers, while others describe covers identical in weight to the normal tan-colored versions.

This auction could be one of those or a photocopy that someone else made on their own.

sauromatian wrote in What the hell is even that?:
Sounds like we were discovering OD&D around the same time? I was lucky enough to find the box (plus Supp.s II & IV) still on the shelves of local game stores (one of which would permanently close soon after), & the rest at Half-Price Books.

Anyone know Thorkhammer's book well enough to describe the contents, or its utility?

Not really.
He frequents DF a lot.

This has some info:
Holmes77 - Dragonsfoot

Zenopus wrote in What the hell is even that?:I also found a box set (OCE) on the shelf of a game store, one that was in Baltimore's Harborplace mall. I then ordered Chainmail and Blackmoor from the TSR mail order hobby shop. Didn't get any of the others until the era of Ebay.

Chainmail eluded me for much longer than it should have. My next step was to go to bookstores & request book searches by the companies which did that sort of thing. I thought Chainmail should have been still available in the late '80s, since it had been in the D&D sections of mainstream stores during the mid '80s. No avail, & I'd have to wait until the usenet newsgroup marketplaces appeared in the '90s.