[ron]

Hello Matt Baker,
And welcome to the forum, that number is proberly the part number for the tow hook, and the other point that you raise about the S? if its in the rear compartment above the hole on the rear wall on the flat rail it may be part of the stamped name of South Australian railways, It would be nice to see a couple of pics when you have the time, good luck with your project,
Regards,
Ron,