On Thursday, October 5, 1967, Bill Graham opened a three-night weekend at the Fillmore Auditorium with a bill that read, top to bottom, Quicksilver Messenger Service, the Grass Roots, and Mad River — a run that would carry through Friday the 6th and Saturday the 7th (per chickenonaunicycle's Fillmore Auditorium list, the Delaware Art Museum, and the Brooklyn Museum, which all give the October 5-6-7 dates and the bill).

The poster is the reason this night is worth stopping on. Bonnie MacLean drew it, and she built the whole thing on a pun. Quicksilver is an old name for the element mercury, so MacLean put the Roman god Mercury at the center of the sheet — winged, liquid, presiding over his own advertisement. It is catalogued as BG-87 in the Bill Graham series (per concertpostergallery's auction records, which also note copies signed by MacLean). By the fall of 1967 MacLean had become the Fillmore's resident poster artist in the wake of Wes Wilson's departure, and BG-87 is a clean example of her voice: dense, symmetrical, literate, happy to make you work for the joke. The Delaware Art Museum holds a copy (offset lithograph, 21 by 14 inches, a gift of Alice and Leslie Schreyer) and the Brooklyn Museum holds another, which is a comfortable corroboration — two museums, the house promoter's own list, and the collector market all pointing at the same object.

The headliner was a hometown act at a particular moment. Quicksilver Messenger Service had been one of the slower-to-record of the first-wave San Francisco bands — no album yet in October 1967, just a growing live reputation built on John Cipollina's tremolo-heavy guitar and the long, interlocking jams the band preferred to tight pop arrangements. A Fillmore headline slot in the fall of '67 is Quicksilver at exactly the stage where the city already knew them cold and the rest of the country was about to. Mercury on the poster, mercury on the stage: the pun is affectionate because the band earned it.

Beneath them, Mad River is the connoisseur's pick on this bill. A Berkeley band — transplanted, originally, from Ohio — Mad River cut a self-released EP on a tiny local label in 1967 and went on to make two albums that psychedelic collectors still prize for their eerie, minor-key strangeness. Catching them as a Fillmore support act in October 1967, before either LP, is catching them right at the hinge. On a weekend sold on a Quicksilver pun, Mad River is the name that rewards the people who kept their old posters.

The Grass Roots entry needs an honest footnote, and the house would rather give you the footnote than a confident guess. "Grass Roots" is spelled plainly on BG-87, but the name is genuinely ambiguous for the period. By October 1967 the Grass Roots that most of the country knew was the Dunhill Records group behind "Let's Live for Today" — a chart act, not a ballroom band — while an earlier San Francisco outfit that had briefly used the name (the group that became Love) was long gone. The sources that reproduce the bill, including the Online Archive of California's listing ("In dance-concert: the Grass Roots, the Quicksilver..."), carry the name without disambiguating it. So we'll say what the poster says — the Grass Roots played the middle slot — and leave the question of which Grass Roots flagged rather than fabricated.

Lights came from Holy See, per chickenonaunicycle; that attribution rests on a single source, so take it as reported rather than as settled. The Fillmore light shows of this period were themselves billed acts — oil-wheel and liquid projectionists who got their names on the poster for good reason — and Holy See turning up here fits the house pattern, even if we can only point to one list for it.

What makes October 5 the right anchor for the day is partly the poster and partly the shape of the week around it. This is the opening Thursday of a Quicksilver weekend, the first time BG-87 was pinned up outside the hall, and the bill stayed identical across all three nights — so the weekend has one object and one story rather than three competing ones. There is no catalog collision: BG-87 does not appear anywhere in the collection, nothing else lands on October 5, and no neighboring engagement's span reaches this date. It sits cleanly apart from the Avalon's own Quicksilver weekend that same stretch of October (the Wes Wilson FD-140, a different poster for a different room), so the two Quicksilver shows of early-October 1967 each keep their own page.

A good psychedelic poster is often a good joke told slowly, and BG-87 is one of the better ones: name a band after a metal, and let a Roman god sell the tickets. On October 5, 1967, the joke opened for business on Fillmore Street.