Key legal question
Whether the incorrect classification into the wrong pension scale is an AHV-analog or IV-specific matter for retroactive payment purposes.
Extracted holding
The misclassification of the disability degree into the wrong pension scale is AHV-analog and not purely IV-specific.
Extracted reasoning
A mistaken pension scale assignment caused by failure to apply the transitional rule on vested rights is comparable to errors in ordinary pension calculation bases and pension scale application.