Harrington & Richardson used the Prefix AT in 1983.
How old is my Topper 88 HARRINGTON AND RICHARDSON GUN serial number
Serial numbers were not required before 1968
"P" prefix indicates 1953
Harrington and Richardson used serial numbers that started with AM in 1974. The company had similar shotguns being built from 1974 to 1981.
"AY" serial prefix = 1982.
1971
1980
No public records- sorry
Az476987
50-250 usd
No way to answer without the serial number.