For valve rectified amps with serial numbers in the 2000s, see these pages.
During the course of 1965, production of AC50s was moved away from Triumph Electronics in Purley to the Vox/Burndept Factory at Erith, which could produce greater numbers. Orders from America were such that a great ramping up of output was required. Triumph eventually moved on to other things - principally PA equipment and some of the smaller amps.
But it was Triumph though, that kicked off production of the solid state rectified AC50 - the AC50 Mark 3 - many examples on this page. Burndept only really got into its stride later on in the year, so there are relatively few amps on this page.
Its amps are distinguishable by the presence of chassis numbers stamped on the aluminium upright of the preamp underneath the input jacks; WIMA capacitors, and heavier-looking transformers, some with solder-tags under chassis.
The new chassis, lacking the hole for the rectifier valve, were the same as the ones that Triumph made for the amps it produced. Other features are described briefly here.
A copy of the schematic - OS/072 - can be found on this page.
Below, a register of amps. If anyone knows of others that have not yet been included, as ever do let me know.