The famous New York jeweler said the offering of 4 million shares at $21 to $23 each will be made in late April or early May. It marks the second time for Tiffany as a public company. It was publicly held until 1979, when Avon Products bought it for $104 million. But after five years and $53 million attempting to cash in on Tiffany’s well-known name, Avon sold the jeweler to private investors for $135 million. The privately held Tiffany sharply improved profits.