Although the number of his works that still exist is even smaller than that of Chojiro, Sokei began to place the seal of the letter 'Raku' (楽 in Japanese character) on the kodai (the base section of a teacup) of his works, that is common to the present Raku ware products.
伝世している作品も長次郎以上に少ないが、現在楽焼の通例となっている高台内の「楽」字捺印はこの宗慶の作品から始められている。