That is interesting, probably happenstance, but the Dingley Act/Tariff of 1897(Rep. Nelson Dingley, Jr. of Maine) may have increased the import of rough bored tubes from Belgium as I've read that 1/3 of the sporting weapons imports were tubes/tubesets from Liege. WWI of course put the nip on the imports but even by 1909 when the Payne-Aldrich act, which was to relieve tariffs on imports, was passed, the American makers were looking very strong at inland sourcing.

Kind Regards,

Raimey
rse