4.25-inch elliptical secondary mirror and mirror mount for large Newtonian (see photo). Mirror was manufactured by Coulter Optical in the late 1970s and is literally like new because it has never been used. The mirror mount has some wear marks on the mounting threads where it was mounted in a previous scope, but is in excellent condition overall. Though unused, the mirror does look to have what looks like a thin "lint shadow" in the coating, a tiny line about 1/4" long where the coating is not quite the same. It has no optical effect and virtually needs a magnifying glass to find it, but I thought I'd point it out.
Secondary mirrors this size typically sell for $350 to $525 for the mirror alone; I'll sell this one, including the secondary mount, for $225 + shipping (PayPal preferred).