The unicode range of circled digits (U+2460 .. U+2468) cannot be converted to, or from, any of the Japanese encodings (EUC-JP, Shift-JIS, ISO-2022-JP), even though they exist there, and I run across them all the time.
% echo ①②③③④⑤⑥⑦⑧⑨ | iconv -f utf-8 -t euc-jp
iconv: (stdin):1:0: cannot convert
% echo ①②③③④⑤⑥⑦⑧⑨ | iconv -f utf-8 -t shift-jis
iconv: (stdin):1:0: cannot convert
% echo ①②③③④⑤⑥⑦⑧⑨ | iconv -f utf-8 -t iso-2022-jp
iconv: (stdin):1:0: cannot convert
% printf "\xad\xa1\xad\xa2\xad\xa3\xad\xa3 \xad\xa4\xad\xa5\xad\xa6\xad\xa7\xad\xa8\xad\xa9" | iconv -f euc-jp -t utf-8
iconv: (stdin):1:0: cannot convert
% printf "\x87\x40\x87\x41\x87\x42\x87\x42 \x87\x43\x87\x44\x87\x45\x87\x46\x87\x47\x87\x48" | iconv -f shift-jis -t utf-8
iconv: (stdin):1:0: cannot convert
What gives?