Historical Identification: Per Dreyer, NGC 651 (= GC 386 = WH I 193, 1860 RA 01 33 34, NPD 39 07.7) is "very bright, eastern of double nebula", the other portion being NGC 650. The position precesses to RA 01 42 20.8, Dec +51 34 52, which is exactly on the northeastern portion of the nebula, so the identification is certain. There is no doubt that what Méchain and Messier observed was the entire nebula; but Herschel noticed that the nebula consisted of two brighter regions slightly separated by a fainter middle, hence Dreyer's assignment of two numbers to the object. Since it is a "bipolar" planetary nebula, that isn't entirely unreasonable, but normally such an object would be given only a single listing, so it is a little confusing, particularly when the normal way of describing the situation is to say that NGC 650 = NGC 651. A more accurate way, as used here, is to keep the two listings separate but say that M76 consists of both NGC objects (as is the case for several other extended Messier objects).
Discovery Notes: As noted at NGC 650 (which see for images of the "pair"), this is one of many Messier objects for which Messier was not the discoverer, but merely a recorder of discoveries by others.
PGC Designation Note: For purposes of completeness, even though NGC 651 is part of a planetary nebula, LEDA assigns it a PGC number; but a search of the database for that number returns no result, so the designation is shown in quotes.
P-K Designation Note: The Perek-Kohoutek designation applies to both parts of the Little Dumbbell Nebula, namely NGC 650 and 651.
Physical Information: Apparent size 1.08 arcmin?