Webley 38/200 markings

[SixShootinSam]

I got me an ugly little war finish Webley last week, and as most of you Webley fans know there are plenty of markings on it.
Is there any source somewhere that will explain all of these?
If not maybe one of you will know:

Right side:
On the barrel there is a stamp that says "3.5 tons", ".767", and "NP"
Also on the frame near the grips it has a broad arrow which I believe is a Navy stamp. Under that is an "E".

Left side:A crown, under that a "GL or G1 or GI", under that crossed swords and under that a P.

Hope someone knows, thanks.

 

[Jim Watson]

"3.5 tons" Chamber pressure of the service load, long tons per square inch.
".767" Case length, inches.
"NP" Nitro Proved
"Crown/GL" London definitive proof mark.

I think the broad arrow is a general British military property mark, not limited to the Navy.
I do not know what the "E" is for.

"crossed swords and under that a P" I do not know what this represents, it is not in my reference but it turns up so often that I figure it is a military proof mark.

 

[SixShootinSam]

Thanks for your information Jim, what does Nitro Proved mean?

 

[Mike_In_BC]

Nitro proofed just means it was tested with smokeless gunpowder. Instead of black powder I guess, old Lee-Enfield rifles got marked BNP for Birmingham nitro proof.

 

[Jim Watson]

Nitro prooved means tested with an overload of smokeless powder.

The Definitive Proof (Crown-GL) was still being done with black powder in those days.