Hi welcome to the forum,
Silver plated, not sterling. Please check out Homan Mfg. Co, your mark looks like it, although deformed and punched perhaps more than once.

HOMAN MANUFACTURING COMPANY - Cincinnati OH
Homan Mfg Company was established in 1847, out of business in 1941.
The firm also had a division which used the trade mark; Richfiels Plate Co. for lower priced plate
http://www.925-1000.com/silverplate_H3.htmlOel.