2x ALRO slide rule charts Philips Audio communications Miniwatt 1960 Holland

Interesting set of 2 slide rule charts, made by ALRO from Holland (1 signed) for Philips from Holland for international use.  The yellow one is for Audio Communications with various specific scales and dB ration conversion on the back. The MiniWatt slide rule is for determining vacuum tubes in (audio) equipment as also sold by Philips. Both use a cursor construction. They are both in very good condition so there are only small signs of use with the smallest crack on the bottom of the see-through cursor which does not affect use. They both measure ca, 18 cm or ca. 7 1/2 inches wide. Check the attached video on how to work your vintage man tool : slide rule operation instructions!