Does anyone know how old these are?
I bought them from a surplus sale at University in the 90's to get an ammeter with an amps range (My multimeter at the time only went to 200mA). I think I paid 25ยข each for them.
They are labelled Type DP-9. The voltmeter is model BDP9VBC1 (3/15/150 VDC) and the ammeter is BDP9ACD1 (1/2.5/10A DC). They both work and are still accurate compared to a $25 multimeter. The voltmeter is low resistance (600?/3002?/30020?), 200?/V. The ammeter burden voltage is 54mV at 1A on the 1A scale.
I love the safety of 150V on an exposed binding post.
I has to take the cover off the voltmeter to fix the zero adjustment so snapped a few pictures of the insides too.