Yeah, that's definitely a unicorn. Not many factory Colt 9's floating around out there, and especially not in original A1 configuration. I like how they pinned the mag block in those guns. I followed along that exact model when I was making my dedicated lower and pinned the mag block in mine too so the block didn't wiggle or budge and ensure reliability too.
Model R6450 was the mid 80's production, but I would imagine that this is one of the later production guns (model AR6450) because it has the shell deflector and the Restricted markings that weren't required until after the ban started on Sept 13, 1994 but this does look like a legit ban era colt and in 9mm.
You can use Colt branded mags, which are made by metalform, PSA had some decent colt style mags for a while but I think that they've been switching over mainly to the glock style and of course, you can mill a slot for the mag catch using factory uzi mags too. (That's what I did--great quality mags and I could get 3 for the price of 1 Colts mag
Is that close enough attention for ya?
You're right about one thing though. I don't like it.
I love it.