The This company was in business from 1954-1994. It was bought out by Enesco in 1994. Registered in NYC and San Francisco. Recognized by its gold diamond shaped sticker with OMC.
Otagiri imported wares from many Japanese kilns/companies. Most were marked with an OMC sticker. However some were produced especially for Otagiri and have an incised mark or a transfer mark with Otagiri. These appear to have been made around the mid 1970's to mid 1980's.
Imports from Japanese Kilns/companies include:
Kozangama (Mino)
UPDATE:
SEIZAN GAMA
***There is uncertainty even among Japanese sites as to the reading.
From comparison of the bone script characters, I am going with Seizan for this and another similar mark.
*These are similar but not exact. Both appear to be Sei in bone script, although on many Japanese sites the mark on the left uses the Ken reading.
Gold Imari (Nagoya)
Meito 明陶
Kutani 九谷
Seihogama 正峰窯
Soma Ware
Tetsusaburo Gama 哲三郎窯 (ARITA)
Shibata Toki 柴田陶器
The Handcrafted Otagiri Original sticker/mark file date Dec 5, 1977~
Incised and transfer marks