Well, since I KNOW everyone is on the edge of their seat waiting to hear how this played out

, I went ahead with the trade.
The 4506 is in nearly brand new condition, virtually no scratches or abrasions at all (I had seen and fired it once before,several months ago when he first bought it, but didn't recall it's exact condition).
Even the plastic grip is nearly pristine. This is the dash-1 version with the oval trigger guard, flash-chromed trigger and hammer, black Novak sights, and has the R1 stamp at the base of the mag well (I've read mention of this,what does that mean?)
It also has the flat backstrap, which I prefer being that these already have such a large grip.
My buddy bought this with just one factory mag, but immediately bought a brand new S&W mag, so I did get two mags (but no box or papers).
I'm feeling like I did OK, and my buddy is happy with the 66, so it's all good.
I was going to try and post a pic, but I guess we non-contributing members aren't afforded that luxury

.
Thanks again to all for taking the time to weigh in.