GR Royal Key

So a new key acquired and preliminary clean. This key has created lots of questions:

1. I have found the same key in William Wallace’s book so can date it roughly albeit I’ll get to that. But the key is identical. I have 5-6 keys with this similar bit shape which are all GR period or obvious linked to a royal cipher. Does this shape and the numbering have a significance? Was this an issue number?
2. The writing on the side says JEPHSON ESQ No333. This I assume is: https://en.m.wikipedia.org/wiki/Robert_Jephson
Would anyone know why he would have a royal cipher key (Parliament?) and if so what period would you date it based on this?
3. What is the significance of the GR hanging from what I can see it serves no purpose and gets in the way?

Any info would be really useful. Thanks