Gitsun,
I bought an NOS tach from Brit Cycle, which is the event that started this thread (there seems to be a recently-discovered cache of these NOS tachs). The tach is good looking, works very well, and is in new condition. There is no redline marked on the tach; the specs from Rupert Ratio's manual shows that the B44 develops 28 hp at 6500 rpm, and a "safe" maximum at 7000. I've added a redline to the tach at 6500 just to preserve the originality of the beast. My bike is a complete rebuild with 5100 original miles on it, and runs smoothly up to 5000 rpm or so, where I usually shift.