This type of earthenware has many theories surrounding it, and marks that have been confirmed include Okei inside a square frame and Okei inside an oval frame.
Theory 1
The theory of Edward S. Morse (a researcher and collector of ancient Japanese ceramics who has greatly contributed to the appraisal of ancient ceramics) presents that this type of earthenware is from around the Kansei era (1789 – 1790) and a type of Bairin ware from Omi Province.
Theory 2
Although the producer is unknown, this type of earthenware was fired in Okei, Uguisudani, Edo around the mid- to late-Edo period.
Theory 3
This theory is similar to Theory 2 in that this type of earthenware is from Okei, Uguisudani, Edo, but it presents that the producer is Sakai Hoitsu, the representative painter of the Rinpa school from the late-Edo period. Hoitsu established Ugean in Okei, where he fired Kenzan-style ceramics under the name of the 4th generation Kenzan in addition to engaging in painting and writing. The engraved signatures and oval marks of “Hoitsu” have been confirmed on these works, but this theory presents that those with the “Okei” mark were also by Hoitsu.
