Discussing stencils of railways, I read about the firm of Thevenon & Cie. who produced sets of letters and numerals for industrial purposes, and by the period pictures, could be also seen in most of the French Army properties.
You're welcome. Now I'm trying to determine the sizes for each application. It seems like the stencils had a limited number of sizes available from the manufacturers, and given that the French army had to distribute so many sets of stencils, chances are that the letter sizes would have been in a limited range.