38 Smith & Wesson round

[kweagley]

Also the barrel length is 5" and there is no landyard ring present or does it look like it had one.

 

[Radagast]

BNP = British Nitro Proof - it has been test fired with a proof load to British standards.
.38" = Caliber
.767" = length of cartridge case.
3 &1/2 tonnes = normal cartridge pressure.
The crown means it has been proofed at a British proof house, one of the establishments that by law proof guns sold in England.
There is a list of proof marks here:
http://www.phoenixinvestmentarms.com/archives/Proofmarks.pdf
Barrel length is correct for the K200.

There was a commercial version of the K200 without the Lanyard ring and with checkered grips. If your gun has checkered grips there should be an uncheckered diamond around the grip screws if the grips are original.