Source: Kaiho Kenjaku (懐宝剣尺) of 1797
Yoki Wazamono (良業物) can literally be translated as "good instrument that plays as it should". It was the third highest of the following ratings:
Saijō Ō Wazamono (最上大業物), "Supreme Grade."
Ō Wazamono (大業物), "Excellent."
Yoki Wazamono (良業物), "Very good."
Wazamono (業物), "Good."
History of the ratings
The terms come from the book Kaiho Kenjaku (懐宝剣尺). The book was first compiled in 1797 at the request of Heisuke Takuseki, a famous sword appraiser and retainer of the Hizen Karatsu clan, together with Yamada Asaemon Yoshitoshi (山田浅右衛門吉睦), an expert test cutter and executioner of the Tokugawa Shogunate. He was the fifth head of the famous Yamada line of sword testers. A total of 163 sword makers achieved wazamono or higher status. Due to its popularity, the Kaiho Kenjaku was republished in 1805 and 1815.1
A major updated list was published in Kokon Kajibiko (古今鍛冶備考) or "Ancient and modern blacksmith notes" of 1830.2
Any test cut is very stressful on a blade, and thus there is a considerable risk of damage. Therefore many old masters were excluded from testing.
1. An original of the Kaiho Kenjaku (懐宝剣尺) can be viewed online in Waseda University Library's Kotenseki Sogo Database.
2. The Kokon Kajibiko (古今鍛冶備考) of 1830 can be viewed online in Waseda University Library's Kotenseki Sogo Database. (A simple viewer is here.)
List of Wazamono (最業物)
See the main glossary article Wazamono (最業物)