Differences from ISO-8859-1 have the Unicode code point number below the character.
ISO-IR 158 is a supplementary ISO 2022 graphical set, containing characters which are absent in ISO-8859-10, but which are required for writing Skolt Sami or historic Sami orthographies. It is intended to be used in an ISO 4873 profile for Sami languages, as a G2 or G3 set (i.e. prefixed with 0x8E/SS2 or 0x8F/SS3 respectively) alongside the main Latin-6 (ISO 8859-10) G1 set.4 ISO-IR-158 and ISO-IR-197 are both referenced in an informative ISO 8859 annex as allowing for a more adequate coverage of the orthography of certain Sámi languages such as Skolt Sámi than ISO-8859-4 or plain ISO-8859-10.5
The code chart gives a symbol used in older orthographies to denote an aspirated consonant, usually written as a reversed apostrophe or raised left-half ring, the unusual name of "high ogonek".6 The table below shows the additional graphical set.7
Standard ECMA-144: 8-Bit Single-Byte Coded Character Sets - Latin Alphabet No. 6 (3rd ed.). 2000. This Ecma publication is also approved as ISO/IEC 8859-10. https://www.ecma-international.org/publications/standards/Ecma-144.htm ↩
Whistler, Ken (1999-10-11). "ISO/IEC 8859-10:1998 to Unicode". 8859 to Unicode mapping tables. Unicode, Inc. https://www.unicode.org/Public/MAPPINGS/ISO8859/DatedVersions/8859-10-1998.TXT ↩
International Components for Unicode (ICU), iso-8859_10-1998.ucm, 1999-10-11 https://github.com/unicode-org/icu/blob/master/icu4c/source/data/mappings/iso-8859_10-1998.ucm ↩
Swedish Institute for Standards (13 July 1992). ISO-IR-158: Sami (Lappish) Supplementary Set (PDF). ITSCJ/IPSJ. https://itscj.ipsj.or.jp/ir/158.pdf ↩
"Annex A: Coverage of languages by parts 1 to 10 of ISO/IEC 8859 (informative)" (PDF). Final Text of DIS 8859-1, 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No.1. 1998-02-12. ISO/IEC FDIS 8859-1:1998 / JTC 1/SC 2 N2988 / WG3 N411. http://www.open-std.org/JTC1/SC2/WG3/docs/n411.pdf#page=12 ↩
Whistler, Ken (1998-09-22) [1991-04-04]. "High Ogonek". Unicode Mail List (Mailing list). https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML013/0211.html ↩