Go to the site proofhouse.com and click on Colt, then click on DA Revolvers it gives a list up to 1978 if yours is newer then that its not a valuable and you will have to contact Colt Manufacturing Co.
Made in 1966.
A Colt Python serial number 35128e was manufactured about 1964
That Colt python was made in 1975.
Your colt python was made in 1975.
The records I found from 1955 t0 1985 do not show a serial number that high for a colt python.
On the butt
You will have to call Colt to find out.
You must call Colt
Call Colt and they will tell you.
The records I have show a Colt Cobra with that serial number made in 1974.
1963
Depends on it's serial number.
Look on the butt and frame