50-100 USD
You will have to measure the inside diameter of the barrel to find out if it is not marked.
serial number suggests a single barrel, hinged frame Model 1908/08 shotgun - if so - 1920-25.
50-130
Harrington & Richardson did not make a Model 1900. Hopkins and Allen did.
50-100 USD
50-100 USD
That would be a Model 732 2.5" barrel, Excellent condition $185-195 - add $25 for 4" barrel.
About $70, depending on condition.
Harrington & Richardson used the Prefix AT in 1983.
I purchased a new Harrington & Richardson 12 gauge model 088 from K-Mart in 1980.
Your harrington and richardson model 900 was made between the years 1962-1973.