According to Sig, mine came from an unidentified Cali PD. From the looks of the slide (not refinished), frame, and internals, my P229 was lightly used while with its previous owner. With a born on date of 2000, it should have a max of 5-6k rounds thru it, and I think a lot less than that.
I would hope that I could catch an academy gun while inspecting it, but maybe not with the factory refurbish and all. Sig says that they will refinish the slides if necessary, but do nothing to the frames. You make a good point on buying with caution, but that goes with all used (not abused) guns. All the more reason to see before you buy I guess.
Wish more LEO were involved with shooting such as you two gents definitely are.
Sigforum.com is a good resource for these weapons, as this great site is for just about everything gun related. Thanks Greybeard!