I have seen various prices for the 999. it depends on overall condition of the piece.
I am guessing, but say good condition, then $250 give or take. That model has adjustable sights front and back........................
36GA
$100, more or less
$100
About $75-90 depending on condition.
$50-$125, depending on condition.
50-200 usd dependingon specifics
Seldom exceed 100 USD
$50-$100, depending on condition.
The Harrington Richardson Topper 12-gauge model 88 shotgun is not worth a lot of money. There are quite a few for sale online for $75 to $125 depending on the condition. This is a pretty basic gun with no pizazz.
Value of ANY gun is based on make, model, and condition. You gave us one of the 3 things we need. There were several models of revolver made by Harrington & Richardson over a great many years. Values could range from $10 to $400.
A H&R 760 in .22 usually sells for right around $100.
Depending on condition, $100-$150.