I get 1983 as a Date. The unpolished finish was done during the Colt Strike of that era, the polishers walked out and they only polished the premium guns. Also The Agent and Commando were first unpolished parkerized as part of huge overseas contracts, some of which never got shipped.Don't worry the internals are (usually)finished/fitted as well as any D frame was. The sights are usually very well corrected for 158grain loads also. This era D frame Agent with the shrouded barrel was pretty much the same as the polished out Cobra of the era.
I'm on my third Agent like that! I wore out(stretched the frame) the first after maybe 3000 +p 158 grain FBI rounds and maybe 500 +p+ 110 grain treasury rounds! (before I knew better). My second one in the middle 80s was tuned to perfection and I shot it quite a bit until I became,er, 'proefficient' with it. Then I sold/traded it to another copper who adored it.He still has it! I found a NIB one in the early 90s after I got rid of the 2nd one and it has smoothed up after a couple thousand careful qualifacation rounds for my CCW over the years. I want to be buried with it!