Jennings Electronic Industries J100
The J100 along with the J40, both solid state, were the first guitar amps marketed by Tom Jennings's new company, initially "Jennings Electronic Developments" (in mid 1968), then "Jennings Electronic Industries" by 1969.
Detailed pics of the J100 above, which is from late 1969 / early 1970, can be found on this page.
On the JEI J40, see here.
In January 1970, Jennings gave "Beat Instrumental" magazine an outline of his thinking:
Snippet from Beat Instrumental magazine, Jan. 1970.
Both amps - that is to say the J100 and J40 - may have been on view at the British Musical Instrument Trade Fair, held in London, in August 1968:
Report from Beat Instrumental magazine, Aug. 1970.
But nothing is said explicitly in relation to amplifiers for guitar. Some of the units will certainly have been for PA and Organ. A picture, claimed to be of this show, has been published in a printed source. Alas, it is of the show the year later - August 1969.
The first definite reference to the J100 comes, however, in July, as a sort of preview of the BMI show in August 1969:
Beat Instrumental magazine, July 1969.
British Musical Instrumental Trade Fair, August 1969. This picture is NOT from 1968 as has been claimed. The J100 is over to the left,under the PA column.
The Shadows in Copenhagen, 1970
Beat Instrumental, February 1970. Note that the J100 was available in three forms - the amplifier as a separate, a combo, and with a D4 speaker cab.
JEI price-list from late 1972.
Jennings J100 amplifier separate (solid state)
Possibly an early J100 - the amps below have a green/grey fascia behind the front-panel controls.
Sold on ebay.uk in mid 2012. A two channel amp with a three-position mid-range boost (a relative of the mid-range boost of Vox solid state amps).
Currently in Germany.