Dec 20 (Reuters) - Old Mutual Plc
* Says OM Asset Management announced today closed its underwritten public offering of 14.95 million of its ordinary shares.
* Says following sale, Old Mutual now owns 51.1 pct of OMAM.
* Says shares were sold by Old mutual at a public offering price of $14.25 per share.
* Says Old Mutual will realise gross proceeds less underwriting discount from offering of $291 million. Source text for Eikon: Further company coverage: (Reporting By Simon Jessop)