Hello 
HepsibarWell, 
Webb has a long heritage and I have been
trying to understand the AUS perspective for some years.
The 
Wasp was the six-bladed 12" model.
It formed a part of the holy Webb 
trinity:
the 
Whippet, 
Wasp, and 
Witch.
I would rate the 
Whippet good; 
Wasp better; and 
Witch great  

[Apologies to Devo fans].
My best guess is that the 
Wasp was a post-war model 
introduced here in about 
1947.
I would date AUS sold machines from that time to about the mid-1950s
[based on newsprint advertisements]
It sold over many decades: -
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/60888/webb-range-1970s.htmlAn image of your machine may help dating ...
Hope this helps.----------------------------------
Jack