On the subject of No4T' FTR's, my father was a National Service armourer 1954 to 56 and he can remember as a lowly NS conscript, getting the very grubby job of removing stored No4T's from their crates after they were delivered on a convoy of army lorries, cleaning off the cosmolineicon, checking them over and test firing them, a very large quantity of 4T's and a very dirty job!

This stuck in his mind because of the sheer number of them and the bloody cosmoline removal....on the job for weeks! None of these had been FTR'd (that he could recall) and they had apparently been quickly checked over and stored after WW2.

I would guess they were replacing examples that were worn out and kept in service post 1945...

He did say that a small number were condemned and striped for parts, scopes etc

A very long time ago now, but it does also add some additional credence that 4T's never went through the massive post war FTR program.