The F7 has the early radiator grille so it must have been one of the original ones. It was nowhere near as popular as the shorter wheelbase F12, and I am sure Dennis historians can let us know when the F7 was discontinued in favor of the F12.
Ed: from other postings it seems to have been soon after 1950. In other words the F7 had a short run as the first was delivered to East Ham 1949. F7 and F12 did not overlap. See picture 40852
MHW800 was a reserve at that time. It was originally at Brdewell and was replaced by OHU229 and went on the run at Speedwell when opened New Year's eve 1951 and its first shout there.
Ed: from other postings it seems to have been soon after 1950. In other words the F7 had a short run as the first was delivered to East Ham 1949. F7 and F12 did not overlap. See picture 40852
Added by Rob Johnson on 23 September 2021.