Hi Malcolm,
I haven't heard of anyone that can decipher the ID plate as the records were thrown out a long time ago.
The 19 Bon Mow looks like it's a fifties model, some info. here
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/65009/model-19-history-record-c1953.htmlIf you had the original engine you could get the year of manufacture from the stamping on the flywheel.
Cheers
Max..