The "best" serial number chronology is in the Second Edition of Walter's book, and it shows the Lewis Model beginning in production during 1901, at 55000, and going to 123677 in 1906. 91919 would still be 1903, but a Lewis Model.

Any of these serial number chronologies are at best a "best guess" and some like the A.H. Fox one that has been kicking around since Lightner Library did it in 1976, are worth just what you pay for it on the internet.