Originally Posted by Storm

Yup, mine is a 4516-1. It has never malfunctioned with hundreds of rounds through it. As said, the original yellow follower mags for the 4516-1 are heavily stamped with a warning to be used only with the 4516-1, and I also have no reason why, but my 4516-1 has worked flawlessly with the other later mags for the gun. I have on occasion been tempted to replace the bobbed hammer with a standard one but have resisted that temptation so far loving the gun as it is.

If I was the OP I'd jump on the available 4516-1. It is exceptionally reliable and extremely accurate. It's a heavy gun, but overall I think that contributes to very smooth shooting. For carry you had better have a stout belt.

I'd also add that with a pistol like this I'd overlook slight to moderate cosmetic issues as these guns clean up beautifully with the use of Scotch Brite pads and Brillo. My 4516 was a mess when I got it and now it looks almost NIB and orginal with just an evening's work. The scuffs and light scratches from carry can be erased. Heavy/deep scratches and gouges, not so much. Steel framed guns offer the possibility of the best results.