Which caps are the most durable for the "51"? How do the gold filled and lustraloy caps hold up with use?

The precious metal caps are the softest -- sterling silver and 14K. The silver caps will get nasty as the rhodium plating wears and flakes off. Gold filled caps are better, though they can brass (though not easily -- the gold fill is relatively heavy). Lustraloy (stainless) are the toughest, though the brushed or frosted finishes will polish from use (and the biggest risk is that darn bright arc from the clip ball's side-to-side movement especially on later pens with long clips). I'd say a Lustraloy cap with Blue Diamond clip is probably the hardiest.

--Daniel

But those Silver caps are so damn attractive

Even if you get a bad one, you can get it de-dinged, polished and even turned into a hammered cap.

I will shut up now and go and take my pills :doh:

Jim