If the entered combination is not encoded in Unicode by a single code point (precomposed character), most current implementations cause the display of a free-standing (spacing) version of the accent followed by the unaccented base letter.
For users with insufficient typing skills this behaviour (which is explicitly not compliant with the current DIN 2137-1:2012-06) leads to mistype a spacing accent instead of an apostrophe (e.g., it´s instead of correctly it's).
The "T2" layout newly defined in DIN 2137-1:2012-06 was designed to overcome such restrictions, but firstly to enable typing of other languages written in the Latin script.
The characters shown at the right border of a keytop are accessed by first pressing a dead key sequence of AltGr plus the × multiplication sign.
Thus, it enables to write several minority languages (e.g. Sami) and transliterations, but is more difficult to comprehend than the "T2" layout, and therefore not expected to be accepted by a broad audience beyond experts who need this functionality.
The current DIN 2137-1:2012-06 simply requests the presence of a "capitals lock" key (which is the name used in the ISO/IEC 9995 series), without any description of its function.
Most Linux distributions include a keymap for German in Germany that extends the T1 layout with a set of characters and dead keys similar, but not identical to the "Outdated common secondary group" of ISO/IEC 9995-3:2002.