Yeah I've had a word with my mate and he's is a 'custom' made watch. He said the crown was not standard! I wish he'd told me that in the first place!!!!Tony,
I've just measured the SKX007 male threads at 3.90mm which surely means a M4 thread?
Will hop out to the workshop and measure a BA 15 in a moI think you need to use a pitch gauge on the thread, it's no surprise that the diameter is similar to BA, as the BA system is actually Metric based (Swiss watchmaking threads) .
A 0.21mm pitch, when the norm is 0.35mm, seems odd - could be wrong though.