As stated, value of ANY firearm depends of oversall condition. Also, what is the age of the firearm ??? That is determined by the serial number.
If I asked "what is the value of a Chevy bronco" Questions would be, when made, mileage, body condition, chrome condition, tire condition, glass condition, accidents ??? etc, etc........
You have to spell it out whatever you want to sell. You will never have a gun shop answer the question because they don't know what the gun looks like............
But, I'm sure a gun dealer would offer you $50-$75 spot cash...........................
Your colt agent was made in 1964.
Blue Book of Gun Values
If your colt is the thunderer model (you do not say) then it was made in 1902.
100-1000+ depending on exactly what it is.
value depends on overall condition.................
value depends on overall condition, model ..................
Colt revolver44-40serial6423103
You need to call Colt
100-1000 depending on specifics
100-1000 USD
value depends on overall condition...........
what model, caliber. ????????