Here's a very rare amp!!! JTM 45 dating to very early 1967, with aluminum chassis, cast block ends, gold "JTM" front panel, white rear panel, era correct circuit specs and....
what appears to be a factory original Drake 784-128 output transformer. The OT is spec'ed for EL34 output tubes, NOT the ubiquitous KT66's associated with JTM 45's. Many might debate this is real or this amp ever existed. I have seen one other JTM 45 with EL34's that was said to be original. It was white and from around this same time period.
There are also a handful of amps documented in the Marstran database with very similar specs.
Disclosure: this OT has been rewound. Not by me, but it was recreated with the original specs.
I have heard that AC/DC, and Angus in particular, favored the earliest EL34 equipped Marshalls. The tone certainly suggests this to be true. But, what I always assumed to be steel chassis "Black Flag" amps, might have also included these transitional beats.
Even with my Les Paul, those iconic tones are there. It almost demands you play those riffs. What a fantastic experience!
Feel free to debate the authenticity. It's what we do. I have documented and dated each part of this amp. During restoration, I replaced many non-original components with era correct NOS parts. Now it has returned to the owner to be enjoyed.