Eric:
So far, I have a little over a year of use on my ZDP Delica. It’s been touched up a half-dozen times, but only once did I get a chip in the edge. I think it was something like your cardboard staple that did it. I recall hearing it make contact with something hard and thinking that there’s be a chip for sure – and it was. I have been staying with 20 dps, thinking the edge would be a little more resistant to chips. Repairing the chip was the only time I had to go below 800 grit.
I’m would bet that your ZDP blade is not a second. I believe that Spyderco buys their ZDP blades finished from Seki, Japan. The ZDP steel is made by Hitachi, but the blades are finished in Seki, which is an equivalent to Solingen, Germany in terms of knifemaking reputation. I’ve read elsewhere in the knife forums that Spydie has a plant in Seki, but it’s probably a particular knifemaker that is contracted with them.