The shotgun frame is an SB-1, rifles SB-2.
NEF branded single bbl. shotguns are 'Pardners"
H&R branded single bbl. shotguns are ALSO called 'Toppers'
BUT, a little history:
The TOPPER moniker originated with the original Harrington & Richardson
which went under sometime in the late 1980's. These arms featured color case hardened iron frames which were used for both shotguns AND rifles.
Calibers offered at various times included .22 Hornet, .22 Jet, .30-30 WCF,.357 Mag & Max, .44 Mag, .45-70 Govt. (don't think I forgot any!)
The company was reorganized as "New England Firearms" at which time all service, parts, even discussion of the original products was strictly forbidden... no doubt mandated by legal considerations.
The latest incarnation of this manufacturer seems to be the buyout/merger with Marlin and now they're H&R 1871...again they will have no part in any products produced during the years previous to the latest reorganization and re-naming of the firm.