I meant no disrespect with my comments, but my evidence is over 770 pics of Diezels archived over the past 20+ years and my participation in builder forums going back just as far. Here's some of the rundown in general terms.
Confirmed in a '96 BF: this amp had a tube in position V2 using both tube halves for the original version of Ch1. Also, V3B was in circuit and used for Ch3 2nd stage, which would eventually be removed in future revisions. As far as external indicators, on the front panel there was only a single 3-pos bright switch for Ch1 on this amp. The input tube was also arranged with a cathode follower, but not for all channels. Plate resistors and bypass capacitors are slightly different values than all amps from the late '90s to current. (Have not yet verified a specific year for the changeover.)
There are transition BF amps (likely late '90s, specific years unverified, again) with the original Ch1 completely redesigned (similar to current). These amps use half of V2 as an input stage parallel to the normal V1 input stage, and have two 2-pos bright switches on the front panel, but also continue to use the V3B for Ch3, keeping this channel nearly the same as above, but with slightly different part values all over the place. The input CF may or may not be in these amps.
As of '00 (and potentially earlier) V2 is no longer installed. Input CF is out of circuit from here, going forward. These amps now have V3B out of circuit, changing Ch3 from 4 to 3 gain stages in the preamp along with a TON of other small changes, especially year to year. This is confirmed in '00, '01, & '04 stock amps. The '02 in the video would be similar to these, with minor changes throughout.
And for another bit of fun, there are also amps out there with original blue faceplates that were updated, per owner request, to whatever the current spec was at the given time they were serviced. There are also relatively minor factory-modded variants of everything outlined above.
