What's the difference between the 1911 and 1991 series?

How to the Mk 70,80, & 90(?) series differ?

A big question.  Here are a few.  Maybe others can add onto this.

1911 - standard gun.
1911A1 - 1926 - mods included an arched mainspring housing, a relief cut by the trigger, shorter trigger pull and longer tang on the grip safety.
70 Series - around 1969 - tigher barrel bushing for accuracy and mods to feed hollow points better.
80 Series - around 1981 - BIGGEST difference ever.  A firing pin safety is added to block the pin if the trigger is not depressed.  Increases trigger pull.
90 Series - ??

Dave  

I think the 1991A1 series was aimed at a "no frills" buyer. (I love mine BTW)
Series '90 was rollmarked on the double eagle slide, it was an attempt to cover the SA/DA market.

ive had 3 1991 slip threw my hands in the past 4 years.they were(are )fantastic basic colt 1911.
i still have a couple goverment models and a kimber ultra carry so im hardly 1911 less but id still pick up a 1991 in a minute for 500 uor less like new slightly used.the 3 i had all had good trigers  but certainly could have used a triger job ...thats all.

The 1991 models used 21st century materials to help hold costs down. Plastic triggers, mainspring housings and grips.

when you consider the most changed out parts on a 1911 are MSH, triggers, and grips, why put high quality expensive metal parts in and up the cost of the gun ???

at least you know right off these are plastic/nylon parts (not bad parts) rather than use a cheap metal part that appears nice but is cheap on the inside.

series 70 no firing pin saftey easey to get a smith  to give it a light trigger pull. Original  exact same gun as 1911A1 .Series 80 firing pin block in the trigger mechanism harder to get a light pull costs more for action job so a good pull is possible. Series 90 XSE models and Defender