Proud to be a geezer... it wasn't easy!
Well, you old-timers have covered the ground pretty well. '68 was year 2 of the San Francisco sound, and I recall its influence well, even in Chicago. That was the year the Jefferson Airplane played their first concert in the Grant Park band shell.
Ah, the gear... Yes, the 1-1/2" wide paisley straps... and we thought they were an improvement

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I too had a Standell, 15" + ext. cab (and not for country music either), but damned if I can remember much about it, whether it was even tube or solid state? I think it was tube, but the memory's not clear, except that the cabs were open-back and not loud enough. It was my first real "pro" rig, though, and I recall that I was pretty proud of it.
B-15's and Bassmans were indeed the pro standard, but all us young smart-a**es agreed they weren't loud enough. I recall thinking that a Showman bottom w/JBL's was the top of the heap and wanting one real bad! Actually, I didn't know anyone who used a Showman head for bass, but I bet it was cool.
After a succession of Voxes, I was playing a '64 sunburst J-bass by then, but lusted for an EB-2 (cherry red). At least up until '68, Chicago had been home to the New Colony Six, the Cryan' Shames, and the Buckinghams. Hollow-body basses were IT in that scene. ...and yes, coiled cords, of course, not sure there were any straight ones.
Those were big vocal bands, and that's what we all aspired to. I learned how to sing and play bass early on, because that was expected. No one has yet mentioned Bogen PA's, 4-channels and 60 watts, if I recall... they were the s***t even before Vocalmasters showed up, though I agree that Shure did take over the local stages once they came around, and remained throughout the '70's.
Also, I think '68 was just before Acoustic amps hit as well. I remember like yesterday the first time I heard a 360, and I knew bass amplification would never be the same after. It wasn't. That was a real turning point ('69?), as I recall. Big touring bands were using Sunn by then but they cost more than a year of college education did at the time.
Being excited at the idea of "solid state", and unable to afford a big Acoustic rig, I tried one of those "TV set-top" Fender Bassman 100's, their first solid state bass head. Oh Boy, was that ever a dog! It drove me to my first V4-B, a few years later.
Prior to Acoustic, the SVT, and of course the big Sunns, we were just glad to be heard at all, as guitarists discovered Twin Reverbs and even larger British products. No bass player I knew before then talked about bass "tone". Either you played with a pick or you didn't... that was the tone discussion

. I do recall that started to change in the '70's, once we could actually hear what the bass sounded like on stage.
Thanks, OP, for the invitation to air all this crap out of memory. It seems funny now, but it was the roots of today's gear obsessions. Too bad in my case it all went the way of my album collection

... who knows where? Actually, I found out recently that the guitarist I sold my Standel to still has it. Maybe I can answer my own questions some day.