While searching the internet for information about the Guitars and Amps that Mike Bloomfield used early on in his career, I came across the following quote:
The moment many in the vast crowd have been waiting for has arrived. Only a few insiders backstage know what the moment portends. The lights on stage go down and Peter Yarrow steps into the center spotlight.
"Ladies and gentlemen, the person who's coming up now ... has a limited amount of time ... his name is Bob Dylan!"
The audience roars as Dylan and the band emerge onstage. There are a few moments of confusion as Dylan plugs into Bloomfield's backup amp, a Guild Thunderbird. "Put that up, man, give Bob a little more volume!" says Michael to Yarrow. "I will, I will," the emcee promises. Kooper tests out the organ with a bracing chord, and Barry Goldberg plays a few bluesy runs on the piano. Then Bob is ready.
This appears to be from a reliable source and refers to the night at the Newport Folk Festival that several members of the Paul Butterfield Blues Band joined Bob Dylan on stage for a set of amplified Rock & Roll.
Posted below is a link to the complete article:
http://www.mikebloomfieldamericanmusic.com/newport.htm
Check out this link, and scroll down, for another photo of the little Guild Amp that "shook up the world".
http://nepr.net/music/2015/07/27/paul-butterfield-plugs-in-and-dylan-follows-suit/