G'day Max
That's pretty interesting.

I've always struggled with the terminology used for zero turn mowers.
My understanding is that the first zero turn mowers did not mean zero-turn
radius [ZTR] that dominate the market today. These can turn within
their own width ... a zero radius.

The first zero turns had a turning radius no greater than their width.
[a big difference to the modern ZTRs].

Max, your patent image reminded me of our own Falcon mower: -
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=69626

Cheers
Jack