ISO 646 (freely available as ECMA-6) defines a framework for 7-bit Latin encodings with 12 undefined positions available for standardisation by national bodies according to local needs (PDF, ref. ISO-IR 170).
A large number of national variants have been in use. The ones mentioned below still enjoy support in Internet Explorer (as of version 9.0).
2 + 1
This version is deprecated; the current official International Reference Variant is identical to ASCII.
The IE implementation substitutes ‘∇’ (U+2007) for the delete character (U+7F).