Your confidence in me is not well placed. I didn’t spot this at all, and not sure I have both types. When I have time, I will check my collection. Often, these “silver bullets” are hard to tell, even sometimes when the bullet jacket is bare, unplated steel. Depends on how well polished the jackets were and the over-all condition of the rounds they are in. I agree 100% that the two you show are different plating. Not sure what the difference is between nickel plating and cupro-nickel plating. Assume it is the amount of copper involved, if any. Some bullets were chrome-plated I think, but don’t know about these two. Never was too good at the differences in metal makeup, as my major interest in cartridges has always been headstamps and history, as in company history or contractual histories. I simply “ain’t” much of a scientist, and readily admit it. When I first started collecting, you may recall since you knew me early on from my “Gun Report” question on material codes, bullets were “brass, copper or silver” to me. All I went by was the color! It was you and Bill Woodin that taught me about GM, GMCS, CN, CNCS, plain steel, etc., etc.
I do know from guns that nickel gleams with a yellow tint, and chrome is dead “white” (and on guns, ugly as sin, where nickel-plating is quite nice looking on some handguns).