I'm a newbie here and need some info. Our local Gander Mt. has some used 4566's for sale. I assume they are police trade-ins, I have not been able to inspect them do to store being so busy due to gun buying frenzy, but they look in great condition. All are stainless, the first one has a silver hammer and an straight back strap and comes with 3 mags for $499. The others have black hammers and arched backstraps and come with 1 mag and they are priced at $449. What is the difference with the hammers and back strap? Does this mean the one is older or newer than the others? This could be my first Smith in 19 years. My first handgun was a S&W 645, got it on my 21th birthday. Wish I sill had it. Friday at lunch I'm going to check them out alittle closer. Thanks for any info.