I haven't put the book up for sale. The spelling "Linthicum" is the original family one, I know someone on this forum who has a collection of more than 50 other spellings. My list of Civil War Linthicums includes six from Illinois all with the 'family' spelling.
I just opened the book to check that signature and it is C.A. Briggs the cartoonist on the Chicago Tribune who did the illustrations.