A few months ago I bought a model 176 12 ga 36 inch barreled shotgun from the H&R classified forums, from the serial number on the frame the gun was made in 1983.  Are these guns rare? i cant find anything about them online, the only thing I am coming up with is 10ga models.  
This is what I got from one of my gun books...
Harrington and Richardson Model 176Gauge:  10,12,16,20 Magnum
Action:  Break open, exposed hammer, single shot
Magazine:  None
Barrel:  32" or 36" full choke in 10 or 12 gauge,  32" full choke in 16 or 20 gauge.
Finish:  Blued, case hardened frame; hardwood pistol grip stock and forearm with recoil pad.
Approximate weight:  8 to 10 pounds
Comments:  Produced from late 70's to mid 80's.  All guns except 10 gauge discontinued in 1982
Estimated value:  Excellent-$110  Very good-$85
It also says there was a 10 gauge slug model with rifle sights and a 28" barrel made from 1982 to 1985.
Spanky