"BA" prefix indicates 1983
Harrington & Richardson did not make a Model 1900. Hopkins and Allen did.
Your harrington and richardson model 900 was made between the years 1962-1973.
2013
Harrington and Richardson made it.
Probably Harrington & Richardson
50-250 usd
No way to answer without the serial number.
"P" prefix indicates 1953
"AY" serial prefix = 1982.
'AZ' prefix indicates 1983
'AY' prefix indicates 1982
S prefix is 1956.