This may be more common than we think ?
I've got this frame lug/engine mount, and although the pic shows the wrong end,
it looks like this may be a breakage, rather than someone cutting it off.
(It sits on my desk here as a display.)https://s22.postimg.cc/xsh4ibehd/Enfield_green_framelug.jpg
This came with some old Enfield stuff, and also included were a few stray bits of frame,
all of which seemed to be cast-offs from previous disasters.
My lugged Norton dommie frames also showed evidences of previous repairs.
There was a reason all-welded frames were eagerly adopted by the motorcycle manufacturing folks ?