Here is a photo of a 60's typewriter with the numbers 2-9 plus a zero but no "one".
Makes sense, thanks.
I gotta go with the typewriter being used HAD A 1 KEY, and for what ever reason the person typing this happened to use the 1 key for the 1st line then after that habit typing took over and they used the lower case l.
Ive come across a few popular 1960 era typewriters that have the 1
http://www.mrmartinweb.com/type.htm#triumph
http://www.mrmartinweb.com/type.htm#brother