Hello Llew

I'm sure resident SB Guru, Mod BB, will have something to say here,
and how you should proceed.

I believe this is a 450431 - an early (first model) single deck, I
guess was made between 1968 and 1972. Well worth restoring!

A History Record is available here:-
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=64933

Hope this helps.
----------------------
Jack