If you are mean the H&R model 158 Topper single shot shotgun?This model was made from 1962-1973.
1901 single barrel shotgun, washingtion
50-100 USD
The Harrington Richardson 20 gauge single shot shotgun, Feb. 27 1900 is valued at $75 in poor condition. In good condition, it is valued at $200.
not sure
H&R / Harrington & Richardson
Seek the services of a good gunsmith
No, Michael Harrington is not single.
Under $100.
50-100 USD
Seldom exceeds 100 USD
Unlikely that detailed sn data has been published.
Value will seldom exceed 100 USD if if great shape.