Was produced around 1916.
if double action revolver it was probably made about 1923
under double action model made about 1920
this question should be under Colt Firearms section
double action colt revolvers 1905 - 1978 Serial # 507493 made about 1925
1877 if it's a Single Action Army. Nothing special about the serial number.
18!
if you double it and then half it, you get the same number again. Mind officially blown.
I found a Colt army special with that serial number being made about 1916.Don.t know the value though it would depend on it's condition.
and the model is..................................
@ 1956
After 1978.
No more than 100 USD