Hi
You might be interested in this page
http://www.tvcameramuseum.org/marconi/marconithumb.htm
and a few notes about the marconi:-
Use of two tubes, one normal resolution luminance and one for the two low definition colour signals. This used a grid giving a definition equivalent to 1.5Mc/s, half the normal definition. This makes use of the eyes inability to see the fine detail of colour.
General Description
Looks like a tall Mk2. It used two tubes. Some reports say there was no viewfinder fitted (3).
References
1. WW September 1954 page 436 and "British Radio and Television” June 1954 page 121.
2. Problems of television cameras and camera tubes, by L.H. Bedford. Journal of the British Institution of Radio Engineers, Oct 1954.
3. Journal of the Television Society, 1954 page 241 and page 503.
regards Brian