signed with love forever true

What is the meaning of " sign" above? Does " sign" mean "signature " of letter or " mark" of kiss in the context?


Joni was the girl who lived next door
I`v known here I guess 10 years or more
Joni wrote me a note one day
and this is what she had to say,

Jimmy please say you wait for me
Ill grow up someday youll see
savin all my kisses just for you
signed with love forever true.
"Signed" is the past participle of "to sign"; "(this letter was/is) signed with love forever true".
Thanks a lot, Pieanne.