[Enamel Bits] Vintage enamel repair

I have a vintage enamel -on-brass pin; it’s one of the Canadian
hearts with a leaf in the center. Part of the shiny, protective coat
has worn off of a small area of the enamel. Is there something I can
put over it to protect it? I have absolutely no experience with
enamel, other than as a collecter of Canadian pins. Thanks in
advance, Evalynne

http://www.beadsuncommon.com