Alloy 42 is a 42% Nickel, 58% Iron alloy that is used because it has a
coeficient of expansion similar to that of glass, so may be used for lead
frames in ceramic packages.

Tin/Lead plated Alloy 42 is pretty standard stuff, but it likely should be
fused (reflowed) or it will not have a good shelf life.  

Hope this helps.

Rudy Sedlak
RD Chemical Company