Webley MkII - nitro prooved?

Hi folks, been a while...

And although I'm still mostly enjoying repairing and shooting Lee Enfields, a new critter recently came to me. A Webley MkII

In great shape, but I am wondering if it's been nitro prooved (proofed?), and I am having a hard time finding clear reference for the marks on it. So... if anyone knows if this "NP" stamp is what I think it is... Thanks in advance for any help!

https://www.milsurps.com/images/impo.../3NecnWU-1.jpg


Other stamps found on it:

https://www.milsurps.com/images/impo.../R1X9uYJ-1.jpg
https://www.milsurps.com/images/impo.../dRJ5KrL-1.jpg
https://www.milsurps.com/images/impo.../pR8GaCg-1.jpg

London Proof House commercial nitro proved stamp.

Thanks Green, very much appreciated!

Not that I want to load that old Webley with hot ammo, but it is reassuring to know that I have some options as far as reloading powders go.