If that's a L, it's in lower-case, not what you'd sign as a middle initial.
Clearly, it's a flourish on the Y in Roy and not a separate letter. It's plain from the typed name that his middle initial is S (his middle name is Stewart). However, it's a little odd that the middle initial does not appear in the written signature but does in the name as typed.
Perhaps the lower case looking L at the end of Roy is how he makes the S for his middle initial..rather than lifting the pen off the paper, he just attaches it to Roy..
Signatures over time tend to get simultaneously more stylized and more lazy with less lifting of the pen. That’s an “S” or it was at one time, morphing into just an upswept loop attached to the “y” in “Roy.”
My bad. Why is the flourish on the ‘y’ not in the yearbook autograph?