Check out
http://doublegunshop.com/info.htm on this site, as it's titled, it has all sorts of useful information. Your not getting much action on this post. If you can get better pictures of the proofs I'll lookup what I can find. That unknown proof looks very familiar, I'm thinking Belgium, but then apparently it has British proofs too. It may be the barels were sourced from Belgium. "Time Laminated Steel Twist" is just their marketing guys stating the obvious. BTW measure both barrels, it's quite common to have two different gauge barrels on the same gun.
Steve
