Bob;
1mm =.039. The difference between 15.9 & 15.8 is 0.1mm or .0039 roghly 4 thosandths of an inch or an I/C choke. I don't off hand recall for certain that is the proper interpretation of those two marks for this time frame. At some point in time it seeems as if the Belgians stamped the bore dia when it came in for proisional proof & then re-stamped it at final proof. Finishing up & polishing the bores could account for this .1mm difference. Choke then would simply mean it is not a cyl bore but has some unstated amount of choke.
