The AC30 is not one amplifier with one date code. Three different companies built and numbered it across six decades, with three incompatible systems and a stretch in the middle with no published codes at all. Dating one starts by deciding which company built it: Thomas Organ in the United States, JMI in Britain, or Korg from 1993.
Why Vox is harder than Fender or Marshall
Vox never kept a serial base. Blue Book of Guitar Values states plainly that the only way to date a Vox is to know when the models were produced, because serialisation records were not preserved. What survives instead is a set of individually dated instruments, published by researchers who own or traced them, and it behaves like a set of steps rather than a straight line. Add the detail that JMI fitted the number plate by hand after the amplifier was tested — the work was done by Jack Jennings — and a serial number stops being a clock and becomes a position in a queue.
Thomas Organ (US, 1966–1970): the leading digits are the year
On US-built Thomas Organ Vox amplifiers the serial number begins with the year: 9 = 1966, 10 or 1O = 1967, 11 = 1968, 12 = 1969 and 13 = 1970. The 1O form matters — that is a capital letter O, and a decoder that reads it as a zero will turn 1967 into nonsense. This system does not apply to any British Vox, and applying it to a JMI amplifier produces a confidently wrong answer.
JMI (UK, 1960–1967): dated points, not a table
For JMI AC30s there is no table at all, only instruments whose speakers carry a manufacturing date. Documented points from voxac30.org.uk: serial 4072 = 2 February 1960; 4447 = 27 April 1961; 4981, 4988 and 5002 = 22 December 1961; 5327 = 24 May 1962; 6097 = 31 October or 8 November 1962; 6507 = 30–31 January 1963; 6887 = 3 April 1963; 7785 = 13 July 1963. The same site's work on the 11xxx series reads speaker codes J, U, K and M as September, October and December 1963.
The method's own limits, in its author's words: speakers are usually later than the last chassis codes, by up to three months; a speaker date is not an amplifier date; nothing is known about how long a finished amplifier sat in stock; before assembly, some parts were simply stock; and the serial plate was fitted after testing. His instruction is to add three to four weeks at least to the speaker date "to allow for final assembly, testing, and the assigning of a serial number".
The speaker code is a speaker date
Celestion codes on 1960s Vox speakers use day, month letter and year letter: 02BE = 2 February 1960, 27DF = 27 April 1961, 29FF = 23 June 1961 and 22FM = 22 December 1961. Two of those are source oddities preserved rather than corrected: the page prints 29FF while its own text says 23 June, and shows 22FM where the same code appears elsewhere as 22MF. Treat the code as a date for the speaker and nothing more, then add the assembly allowance above.
Component codes on Vox
Potentiometer and capacitor codes work the same way as anywhere else: 1376623 = CTS, week 23 of 1966, and 235-7017 = Mallory, week 17 of 1970. They date parts, not amplifiers. See pot codes for the general caveat that pots are often stamped ahead of the date they were used.
Gaps we do not paper over
Around ten JMI chassis in the source material have no readable serial number at all — numbers in the 30xx and 035xx series. The VSL, Dallas and Rose Morris years (1967–1992) have no published codes, and neither does the Korg era from 1993. One correction for the record: our own earlier research notes listed a month-by-month AC30 Twin chart as sitting on dsgb.net; that chart is in the Elyea book rather than on the page, so we do not use it.
What this means in practice
Decide the era first — panel and logo, cabinet covering, valves and transformers are what separate JMI from Thomas Organ from Korg. Then apply only the system that belongs to that era: a Thomas Organ prefix, a JMI dated point, or an honest "no published code" for the Korg years. Enter the number in the Vox decoder and it will return a year or a decade with a confidence level, and if your AC30 falls in a gap it will say so rather than guess. Background on the model is on the AC30/6 Twin card, and the sources behind these dates are listed on our sources page: voxac30.org.uk, voxshowroom.com, Blue Book of Guitar Values and hendrixguitars.com.