Sorry to be so long in answering your questions, but I'm here now and will give you the dates of manufacture.
For # D197xxx, manufactured in late 1979.
For # B993xxx, manufactured in mid-1975.
Savage began their "letter series" serial numbers in 1969 with the letter "A" which ended in 2002 with the letter "G". At the same time, they reverted back to 6 digit serial numbers preceded by a letter. Here are the approximate dates of the changing of one letter series serial numbers to the next letter series serial numbers:
The "A" series ran from 1969 through early 1972,
The "B" series ran from early 1972 to mid-1975.
The "C" series ran from mid-1975 to mid-1979.
The "D" series ran from mid-1979 to sometime in 1982.
The "E" series ran from sometime in 1982 to February of 1987 for sure. However, my records are very "thin" at that point and it appears to me that the "E" series finally ended in 1989 because I show a very low serial number in the "F" series in 1990.
The "F" series ran from 1990 to November of 2000 for sure (#F9262xx).
I have no serial numbers for 2001, but my records shows a very low serial number (G050xxx-Feb.) in February of 2002 and final entry (G037649-June) in June of 2002.
I hope this information is of help to you.
Strength & Honor...
Ron T.