The information I have shows that your colt trooper was made in 1961,but it does not show the B prefix to a serial number.
1966
The Colt Trooper MK III .357 with serial number J11918 was manufactured in 1975. Colt's production of the Trooper MK III series began in 1969 and continued until 1983, with serial numbers indicating the year of production.
You will have to call Colt with the serial number.
You can find out at Proofhouse.com in the Colt tables.
What year is a trooper mark 3 serial 10192j.With the serial number that you have provided,your Colt Trooper mark III was made in the year 1975.
Based on proofhouse.com that trooper was the 7th made in 1967 as the productions for 1967 started with serial number 59800.
A Colt Python serial number 35128e was manufactured about 1964
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your colt trooper was produced in 1968.
your colt trooper was made by colt in 1961.
Impossible to answer without the serial number.
1967