'SM', 'S.M.' or 'S/M' and what it means!

[David_Hayward (RIP)]

I am conjecting at the moment that the War Office then Ministry of Supply had written Volumes with different contract types, If that was the case, perhaps '243' was the Volume or series for vehicles, or wheeled vehicles, then the next was a sub-series, followed by a sequential number which started probably post-Great War...it seems that by the early 1930s they had got to V.2400 or so, and they just added as each contract was let? I know that the 'V.' series ran into the 5000s, but whether the 'T.' and 'S.' series used the same numbers I have no definitive proof but the evidence that I have suggests that they were a seperate series.