I think for the -10, too (and that was possibly the initial use, given the 36 wide lamp array - or, at least, they had the -10 usage in mind when they did it). I looked at my DECsystem-10 manual, and I suspect that at least the DF10 (channel), RP10 and TM10 controllers used it (4 rows of 36 lights, in the same aspect ratio), and maybe some of the memory cabinets (MB10, MD10) too - they have the right size, etc but have 4 switches in the lower left corner. Noel