I agree completely.There must be many European stencils, just like there were in the USA. It looks like Holton bought them for a few years, until getting their factory started in Elkhorn, Wisconsin to make their own full line of saxes.
The 'Beaufort', 'American Beaufort' and 'The Special' were Holton brands (and a Holton / Conn brand at the beginning thirties). Mostly stencils (not always!) they are marking extraordinary circumstances. What I've found out with the help of all Holton experts on SOTW until now:
Brand / Year of manufacture / Manufacturer / Reason
'Beaufort' / ca. 1916 - 1917 / Evette-Schaeffer (assembled in Austria?); Buescher / Holton completed tooling for own production 1917
'Beaufort American' (1) / 1918 -1919 / Buescher / WW I induced discontinuity of production
'Beaufort American' (2) / 1921 / Buescher / C soprano; Holton began own manufacturing 1922
'Beaufort American' (3) / 1931 / Holton (Own Couturier); Conn / sellout during depression
'The Special' / ca. 1944 / Lyrist - A. E. Sax* / WW II induced discontinuity of production
All these models are marked 'Chicago' although the company moved to Elkhorn spring 1918.
* This is new insight after a long research. 'The Special' is not made by Couesnon as I previously suspected.