I've been doing a bit of research on the YDS/YM stuff, and the YA5 and YA6 names keep popping up.
I know that they're very different to the YDS/YM, but they've roused my interest, particularly the YA5 and the extent of it mechnical relationship to the later AT1.
This is the closest that I've gone to finding a decent pic of a YA5.