John Herschel discovered NGC 643 = h2435 on 18 Sep 1835 and logged "eF, R, vglbM, 40"."

In 1957, Gerard de Vaucouleurs concluded (based on Mt Stromlo plates) that NGC 643 was an outlying cluster of the Small Magellanic Cloud and not a galaxy as listed in the 1932 Shapley-Ames Catalogue. Eric Lindsay independently listed it as a new cluster (not making the connection initially with NGC 643) in his 1958 paper on SMC clusters and described it from a 30 minute ADH plate (South Africa) as "a conspicuous object, clearly recognizable as a cluster with 20-30 faint resolved stars. The texture and distribution of the outlying stars suggest it is globular; otherwise it would have been classified as certainly open." NGC 643 was deleted from de Vaucouleur's 1964 Reference Catalogue of Bright Galaxies and Alan Sandage's 1981 revision of the S-A Catalogue. RNGC gives the type as 28 (cluster in the LMC) instead of 29 (cluster in the SMC). NGC 2000.0 classifies it as a globular cluster. NGC 643B = ESO 029-053 = PGC 6117 is misidentified as NGC 643 in the RC3 (letter designation from the RC1).

600/800mm - 30" (11/6/10 - Coonabarabran, 264x): fairly faint, moderately large, round, 1.2' diameter, broad weak concentration without a distinct core, some mottling but no resolution. Located 8.5' NNE of mag 8 HD 10041. This object is an outlying cluster of the SMC in its extension on the southeast side.

Notes by Steve Gottlieb