An honor given to 郷士
■ In 土左（とさ） modern 高知県（こうちけん）, the 白札 was an honor given to 郷士（ごうし） in recognition of service. 郷士 (farmer samurai) in 土左 were not allowed to become 上士(じょうし), and 白札郷士 was the highest social class they could attain. The 白札 class itself was called 白札格（しろふだかく）.
□ Literally, 白札 means a white tag or strip of paper. According to 大辭典（だいじてん）, such tags were used to mark winning entries in art exhibitions. The connection, if any, between this meaning and the social class rank is unclear.
◇ See 武市瑞山（たけちずいざん）, a famous 白札郷士。
The above site contains the following sentence:
This entry was created by Benjamin Barrett.