Would need the serial number to answer.
rc46661
You will have to call Colt to find out.
Proofhouse.com has Colt serial number tables.
No serial number provided.
After 1978. You will have to call Colt to narrow it down further.
The Colt lightning 1877 model with serial # 47357 was produced in 1883. (40000-47999)
Call Colt with the sn and they will tell you.
if you have a letter 'C' after the serial number then mfg. date would be about 1960
No way to answer without the serial number.
You will have to call Colt with the serial number to find out.
You will have to call Colt
your colt trooper mkIII was made in 1978.