I had just been looking thru Wirnsberger & came bact to post, but Larry had beat me to it. I think he has nailed this mark. To add a little more begining in 1897 the word "Choke" was used rather than the "Non Pour Balle". A gun having rifled choke was marked "CH B RAYE". Non Pour Raye does not seem to be a viable mark.
Also according to Wirnsberger the first smokeless proofs in Belgium were carried out in 1891 with the proofmaster having the option of using EC or Schultz powders & the bbl would be so marked with the rampant lion over either EC or SCH. Later the lion over PV replaced these marks, but haven't found the date yet.
This would seem to indicate the original Belgian proof between 1891-1897.
