The "T" means it is a tenor.  The "L" stands for low pitch, meaning it is playable to modern tuning standards.  The 1119954 is a patent number that was put on Conn saxophones after 1914.  The M203569 number is its serial number, which indicates a production date of 1928.  There is some market demand for that model and vintage, but its value depends on a number of things as outlined to the lead poster.  Start with the site linked in that response, considering all the caveats very carefully.