Help identifying choke...

[Jordan]

The image is of the tang of the barrels belonging to an old richland arms sxs 20ga. I do not know what choke the barrels are and have no clue what the numbers mean. It looks like one barrel is marked 15.7 15.3 and the other is 15.7 15.6. Anyone able to decipher this?

 

[Jordan]

Found my own answer online. However, since no one here seemed to have the slightest clue (0 replies) maybe I should share what I found in case someone else brings up this question in the future....

someone enlighten me about metric chokes ? Shotgunworld.com

Essentially I subtracted the two numbers, lowest from highest (15.7-15.3 = .4 & 15.7-15.6 = .1) and then put the results into a converter and followed the choke chart link. Thus I have Improved Cylinder (.1 barrel) and Modified (.4 barrel) chokes.

 

[Bfish]

Yeah, basically what Jordan is saying... I've mainly seen English guns like this. A lot of those guys will talk about 3/4 choke as opposed to full and other junk. Those guys across the pond are a little odd!