William Herschel discovered NGC 3667 = H III-531 = h3340, along with NGC 3661, on 27 Mar 1786 (sweep 548) and noted "cF, vlbM, stellar." JH recorded "pF; R; 20"; has 3 stars 10 mag near it, with the two following of which it makes an equilateral triangle.

400/500mm - 17.5" (3/29/85): moderately bright, very small, round, small bright nucleus. Forms a close pair with NGC 3667A = MCG -02-29-026 1.1' E. The companion appeared faint, very small, round, low surface brightness. NGC 3661 lies 10' W.

Notes by Steve Gottlieb