Thanks to John, pictures and details of his superb find: an AC100 SDL speaker cabinet and trolley from late 1964 - one of only two known at present. The trolley is of the earliest type (mark 1) with narrow parallel bars and a basket top for the amp to sit in. The date codes of the Celestion T1088s are "15KJ" and "16KJ" = 15th and 16th October, 1964.

Date code "15KJ" - 15th October, 1964, which relates of course only to the manufacture of the speaker, not the cabinet as a whole.

JMI made very few AC100 SDL cabinets and trolleys in 1964 - four in early August (two for The Beatles), and no more than six later in the year. They were reserved for loan and promotional purposes - see this page.

On 27th October 1964, that is to say not long before the production of the cab pictured on this page, the design was submitted to the old Patent Office in London:

Pictures taken for JMI at some point in October 1964. The cabinet is probably the one that Brian Jones had in Paris and Brussels, 20th and 21st October. The amp is of the new thick-edged type.

At least one of the early SDLs went to Thomas Organ in America in early 1965 (also for promotional purposes) - that is the other that survives, pictured here.

In terms of sales, AC100 SDLs did not really get going until mid 1965, and then mainly in the USA and Europe. In the autumn of 1965, The Who was still the only major band in the UK besides The Beatles to have its own, though it has to be said that Pete Townsend's amps and cabs were occasionally borrowed from/provided by JMI. AC100s for bass and PA sold much better early on.

Dimensions

Trolley - tubing is 3/4" in diameter. Standard (later) AC100 trolleys have 7/8". The basket top measures 17 3/4" x 10 5/8" (outer dimensions); the outer edges of the parallel side and top bars are 6 3/4" apart. Standard production trolleys are 9". The original casters have been replaced.

Cabinet - constructed of baltic birch ply: 39 3/4" tall; 27 1/8" wide; 11 1/2" deep. Sides, top, and bottom are 3/4" thick. The corners have plastic protectors.

Wiring - in "evolutionary" terms, the arrangement represents a step towards the standard scheme of later cabs. Gone is the heavy-duty cabling of The Beatles' cabs and the cab accompanying AC100 serial number 225:

A detail of serial number 225's cab. Further pictures can be found on this page .

Instead, there are runs of twisted green and yellow wire (7/64" diameter, 24/02 gauge), as in standard production SDL cabinets. But two pairs of 1uf capacitors are still used for the cross-overs for the Goodmans Midax horns (to protect them from damage by lower frequencies). Later cabs have a single 2uf capacitor per compartment.