Dear Earl

Good ductile additive/P  free Nickel base covered by a flash ~
0.05 microns of Gold should provide a very cost effective finish
competeitive with HASL and others.

The key component for solderability and shelf life is the Nickel undercoat.
~ 5 microns is adequate if ductile etc as above.

Under proper controlled condition this finish should give all advantages as
1. Longer shelf life - ( Nickel is critical.)
2. Flat surface profile

what more - economic and looks good too.

Anil Kher