How do i fix leaded glass windows? i'm pretty handy but i found these inserts for an oak door and some one

told me if they are lead frames i can slive the joint and peel back and insert new glass…but not if they are zinc how do i know if they are zinc…they are about 4ft by 21/2 feet all(4) with a tulip pattern any ony ever see these and are they valuble?