Pauline, Fabricating a box latch requires skill and will take a little
time to get it right. It is also very satisfying when you do get it
right and everything snaps together just perfectly. Why not show off
your craftsmanship by using gold for the tongue? It is a lot more
springy than sterling, easier to work with than nickel, and easily
recognized as a "quality" part.
Allen Revere's book, Professional Goldsmithing, illustrates step by
step how to make this clasp. It is a wonderful guide to improving
your technical skill.