Max Wolf discovered IC 3555 = W. IV-223 on a Heidelberg plate taken 23 Mar 1903. The identification is certain.

900/1200mm - 48" (4/7/13): IC 3555 is faint, 20"x10" HII region in NGC 4559, extended NW-SE, situated 1.8' NNW of center in the halo. IC 3552 is a fainter, extremely compact HII knot less than 30" NW that was not seen.

Notes by Steve Gottlieb