This is the Supro 6920, which is a very different amplifier than the 6420 thunderbolt. Note the similarities between this amplifier and the Harmony 525. The S6920 often shows up on eBay, craigslist and other places as "The Supro Thunderbolt." It is not. This amp has the logo "Thunder Bolt" as two words. The S6420 was always had the single word moniker even though it was printed as two words seperated by a lightening bolt. While not necessarily a bad amplifier it is not The Supro Thunderbolt. The 6920 Thunderbolt shares cosmetics and cabinet layout with the Supro Corsica. They are sometimes confused with each other as they do bear a strong resemblance and most people are not especially familiar with either amp.
You often see this amplifer advertised in connection with the Jimmy Page sound. While no one has been able to provide conclusive proof regarding the amplifer used to produce the sounds used on the early albums, it is a safe bet that this is not the one.
Valco had merged with Kay sometime in 1967. By 1968, the company was in financial difficulty and declared bankruptcy later that year. Based on what I can find out, the S6420 was produced until the spring of 1967. The Supro Amplifier line was re-vamped in 1967 with new circuits and new cosmetics. The Blue-Green forward facing control panels came out at this time. The S6920 was released sometime in the fall of 1967.
The cabinet of the S6920 is 26 1/2" x 20" x 10". The cabinet is a straight sided box with a chamfer on the front upper edge to lead into the control panel in much the same style as Fender. The chamfer is different than that found on the Fenders, it goes much further down the face of the amp. The speaker baffle is roughly 18" x 18" and is covered in the same silver material as was found on the original thunderbolt. The volume and tone knobs must have fit poorly, because almost every example you see has mismatched or different knobs. I believe that the knobs on the amp in this example are the stock knobs. I have seen more of this type than any other.
I had originally surmised that the 69 in the S6920 indicated a design or release date of 1969, but it appears that this is not the case.
As can be seen, the chassis on this amplifier is completely different than that used on the Thunderbolt or H420. It appears to be the same as the H525 chassis in size, but the layout is different.
