There appear to be two different styles of Colt Series 80 full size Government Models. One is a pretty standard looking gun and the other is upgraded hammer,grip safety etc. What is the story and is a like new stainless steel version of the upgrade worth $600?

I believe you're talking about their "1991" models & their premium line, both Series 80 design.

Are they worth the difference? IMO, yes. I count highly on how a gun looks, I don't really want a matte finish on a gun costing that much.

There's also the option of going to a Springfield Armory, usually about $50-100 cheaper than an equivilent Colt.

Para Ordnance now makes single stacks as well.

You could also buy a used Colt & save a few bucks. I buy most of my guns used.

Not sure when exactly they introduced the "enhanced" model.
That may be what JMoulin is refering to.
A few cosmetic changes, like the grip/trigger guard juncture being relieved for a higher grip.
I think the enhanced models all use the Gold Cup cut on the barrel hood too.
Also, the serial numbers weren't stamped in, being more like pixels.
My 1991-A1 in SS was very drab and didn't look quite right so I stripped it down, masked it off and glass beaded the sides.
Much better now.

I'd say that $600 was a pretty good buy. Get it and give us a range report

I own the series 80 gov model MKIV to be exact    and my original finish was a polished blue till i had it hard chromed the xse models and defender which i also own are series 90  600 hundred is a little pricey ky imports has the 1991A1 with the new roll marks for $639 for the ss gov and commander the matt blue with the standard trigger is $549