Your appraiser probably is not all that far off. From a user standpoint the Colt mags can be a drawback being many 191 owners will put stock mags up and get better ones from any one of a few makers. It does look like the sights look like theywhereput on later but I'm really not enough of a Colt guy to say that with 100% confidence.
As a collector piece it does not look to have been refinished and that is a good thing. Aftermarket finishes can bring value down.
Bottom line is the weapon is not that old so unless one was to find a collector with a hole that only that weapon could fill it would get what used Colts bring these days. Colts run a litle higher than some others mainly because they where the guys to bring us this wonderful design that has taken the world by storm and it does not look like any pistol will remove it from it's throne any time soon. Most Colts I've shot and/or owned have been very nice pistols. Reliable, accurate, and just plain good looking. With your post worded as it is I'm guessing you are looking to sell it and are fishing for a price. I would look to sell it to a person and not to a shop.
You will come out much better 95% of the time. You might try looking at gunbroker
and see what ones in similar shape are selling for. Check to see if any are in your area as geography can have a lot to do with what a firearm will bring.
You have a real nice pistol there. It was me and I didn't have to I'd surely not be looking to get rid of it. It sure wont get any less valuable over time as long as it's being taken care of.