This special version of the model 400 chronograph has a pulsimeter scale. Many watches from the past with this scale were used by medical professionals like nurses and doctors, thus we refer to it as the "Doctors Chronograph" It is only available in the black dial version as an option. The pulsimeter replaces the tachymeter or tachometer scale which is what we normally have on this model.
How a Pulsimeter Chronograph works:
The pulsimeter scale shows at a glance the number of pulse beats per minute. The observer releases the chronograph second hand when starting to count the beats of the pulse and stops at the 30th, the 20th, or the 15th beat according to the basis of calibration indicated on the dial. With the RGM model 400 it would be the 30th beat. The chronograph second hand shows at a glance the number of pulse beats per minute according to where it is stopped on the pulsimeter scale.