My 26-inch 12ga special-order VLD 1899 Francotte with Siemens Martin Steel has two choke markings on each barrel. Closest to the flats is 17.9 over 18.4 on the right barrel and 17.7 over 18.4 on the left barrel. Adjacent outside these marks is 17.9 over 18.2 on the right barrel and 17.6 over 18.2 on the left barrel. The muzzle measures .710 right and .700 left (modified and full). I'd appreciate comment/speculation concerning the two markings for each barrel, please.