A .718" bore - .036" of choke would equal a choke diameter of .682" or 17.32mm. Your gun does not show this marking which is why I say the markings do not indicate the amount of choke, only the word choke indicates it originally had choke. There could have been a slip-up, but under Belgian proof laws this was normally applied only if the bbl had at least .2mm (.008") of choke. Bores have likely been honed & quite possibly the choke in the right bbl reduced.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra