1978
Only Browning knows. Information not in the public domain.
100-1000 usd
It was made in 1977
The 2 letters PP in your serial number sequence indicate that your Browning BT-99 was made in the year 1988.
Browning originally made the Model BT-99. Later they discontinued the bt-99 and came out with the upgraded model bt-100 with drop out trigger and other higher end accessories. As usual all good things must come to an end and they re-introduced the BT-99 again. The exact reason is argued over and over but was basically a demand issue which had fallen off. The Bt-99 was both cheaper to manufacture but to sell as well. There is numerous upgraded BT-99's floating around and still being made which pretty much memic the BT-100. Get your wallet out.
100-1000 USD or more depending on specifics.
It was made in 1971
Made in 1970
Call Browning with the serial number.
No
Browning.com has a sn function listed under customer service.