Just one thing I would like to add.
The very old Lockwoods, 40-50 years old are also very hard to SPP (Bogs will get them). They are also made to tight tolerances.
I get old fence posts from time to time for firewood and sometimes they come with a lock on them. I've got one that took me over a year, on and off to SPP it (Bog didn't work). Then two months to do it again, then six weeks and I'm now into week two with no success yet on the fourth try.
I'm doing a writeup on it as it isn't branded (pretty sure it's a LW) and has a hi sec core. probably hasn't seen a key for 50 years.
When I next get it I'll PM you and maybe send it on. See what you think of it.
I'll post about it soon.
For every expert there is an equal and opposite expert.