The Censor 932 CPU architecture has one instruction type that takes a 3-bit "index register" field, but looking at the rest of the instruction set, I can't see any instructions that read, write, or otherwise manipulate index registers.
One of the possibilities that occurred to me is that it may just be that index register 1--7 are shadowed onto general register 1--7, but I hesitate to bake that assumption in to my emulator code right now.
Edit: The Censor machine architecture started out as a Standard Radio & Telefon machine in 1967-1968. In 1971 the computer division was split off and merged into Stansaab. In 1973, Facit's terminal divison was merged in. And in 1978, it was merged into Datasaab.