[Doesn’t say much in the Japanese wiktionary](https://ja.wiktionary.org/wiki/%E4%BB%A5) (actually mentions a different theory in detail), or anything else in Japanese for that matter. Probably because what you have is merely an 異体字 of 以 and no one really cares.
It’s a pretty rare kanji, it looks like a bushu but it is not. It looks like it is the original kanji for 以. Explanations (in japanese) [http://huusennarare.cocolog-nifty.com/blog/2014/07/post-598f.html](http://huusennarare.cocolog-nifty.com/blog/2014/07/post-598f.html)
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[Doesn’t say much in the Japanese wiktionary](https://ja.wiktionary.org/wiki/%E4%BB%A5) (actually mentions a different theory in detail), or anything else in Japanese for that matter. Probably because what you have is merely an 異体字 of 以 and no one really cares.
It’s a pretty rare kanji, it looks like a bushu but it is not. It looks like it is the original kanji for 以. Explanations (in japanese) [http://huusennarare.cocolog-nifty.com/blog/2014/07/post-598f.html](http://huusennarare.cocolog-nifty.com/blog/2014/07/post-598f.html)