I take it this was a rear catcher model as I believe all or most of the side throw models are steel chassis.
The professional catcher models are not that rare but not that common either. I have come across a couple on EBay in the last year ( one push model in Sydney and a self propelled one on QLD).
Also found a self propelled model on Gumtree recently for sale just outside Sydney.

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!