"SECAM was 625 lines like PAL [...]"
The French had every intention of introducing 819 line colour TV. The Mullard touring lecture about the forthcoming UK PAL system was accompanied by a data sheet - which might still be in a drawer. It described in technical detail how various colour TV systems worked and their problems compared to PAL. IIRC the technical descriptions included the mechanical "banana tube", NTSC, PAL, and SECAM using 819 lines.
From the Wikipedia article on the history of SECAM:
"Work on SECAM began in 1956. The technology was ready by the end of the 1950s, but this was too soon for a wide introduction. A version of SECAM for the French 819-line television standard was devised and tested, but not introduced."
The banana tube was really an anachronism - yet was the subject of an IEEE paper in 1961.