Browning.com has sn data under customer service.
100-1000 usd
No serial number = no way to answer.
It was made in 1971
Made in 1970
Call Browning with the serial number.
The 2 letters PP in your serial number sequence indicate that your Browning BT-99 was made in the year 1988.
Believe that your serial number is incorrect. There are no BT99 serial numbers that start with 47. There are however serial numbers that begin with 74 which is the year (1974)that they were made.
The bt 99 seril # is read as follows if one letter it is an early one like : 2xx d 8 . It was made in 1968. Later they included two letters and the following number is the year made.
Go to Browning's site, click on Support then date your firearm.
1987
1971