cross member stencilled/painted markings

[JonE]

could it have any other meaning (now that we also have seen Biddlecombe's car with S and similar N?) Are the stamp sets definitely different for the two words SLN and AUSN... otherwise why wouldnt the operative have just used the N he had just picked up oreviously... unless he had intended something different? Approximately what year are we now, Tony - 1929?

If he had stamped a Z it would be of different proportions, wouldn't it? Maybe just because of camera angle....