Vox AC30: Burndept chassis colour codes for voicings
Treble, Bass, Top Boost
1964 - early 1968
From around chassis number 3000, Burndept indicated the "voicing" of the chassis it produced for JMI not only with a stamp in red, but a colour code. "TREBLE" had a red splash; "T/B BOOST" (integrated treble and bass controls on panel) had green; and "BASS" - produced in smaller numbers - had blue. "Normal" AC30s had neither stamp nor colour.
The splash of colour was presumably supplied - while the chassis was on the assembly benches - to indicate how the voicing should be stamped above it.
A page on Burndept chassis numbers can be found here.
Detail of serial number 11613T, chassis number 3083.
Serial number in the 12000s, chassis number 4530.
Serial number in the 18000s, chassis number 8407.