Cylinder blocks for all the major manufacturers were similar.
Its just that on a forum not a million miles from this one, some 'expert' is venturing that dommie cylinders were sleeved.
With 5mm thick sleeves too, if you please.....
If that were true, refurbishing a worn out set of cylinders would be simple simple simple,
instead of the dire shortage of good cylinders we have today,...
(Myth busted ? = fiction)
A good engineer does for a bob what a designer does for a quid..
Nortons had to be careful too they didn't infringe Triumph patents.
Nortons inhouse engine man had done quite a straightforward design of twin,
but it looked a lot like a Triumph design. Quite a lot !!
So they bought in Bert Hopwood to do something that was different enough to keep them legal.