macs_07 wroteThanks Martin.
That is very helpful. Interesting as to where both Tonks & Mallet fit.
Pity the full patent is not available with pictures.
You can download the full patent by using espacenet. Just ask for advanced, and then enter GB190925078 as number.. You can then copy the full specification by using the download function. Any problems, contact me, but I am computer illiterate, and still manage it!
If you are overseas, perhaps Mallet was importer?
I am still amazed that Yale keyways were sawn for quite a period, presumably by a jig saw and hardened gude plate.
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