Hang on - you say these are 8-way RJ11s. Do your UTP connectors just go straight into the socket OK?

These might be ISDN wallplates with a pre-wiring PCB - they do use Krone connectors after all: these are pretty horrible excresences designed to make it "easy" to DIY ISDN installs. They are, however, sod all use for anything else since the pre-wire PCB grounds together certain leads so allow a good reference for the incoming exchange signal (in spite of them supposedly being differential).

You said there was a label on the back, can you scan or re-draw it and post it?