Correct Buckstix, Massart was probably in business much before he applied for a patent.
Per the "qui est qui" there was a A. Massart in Liege in 1886 and then in Herstal (next door) in 1892 who applied for patents at those dates. Plus the one in Henne-lez-Chaudfontaine who applied for the 1902 patent. They certainly could be one and the same.
I still believe that your double is circa 1890-1900.
Best regards,
WC-