[Mike Kelly]

A nice job !

I have a black one similar to yours, it has a 1950's era Aust. army power supply inside the little battery cabinet. The power unit is switchable from either 240 mains or the battery/vibrator.

I've seen the BC 221 in a different style of case, i.e. finished in a olive green colour. There were many models and the final number made would have been mind blowing.

These were a nice bit of kit, mine is still a accurate instrument . I think each unit was tuned at the factory to match the reference xtal and if you swap the xtal over from another set , the calibration book will not be accurate . I have read that quartz xtal's deteriorate over time and the reference xtal might change frequency slightly , don't know if that will have any impact on the accuracy.