A somewhat unusual EQ/Filter

I recently came across this filter. I have never seen anything like it. Have you? Made in Denmark by the very small, now long gone, company NP Elektroakustik. It has a low section and a high section. Both offer shelving boost and a highpass / lowpass control. Funny thing is that it works only on fixed frequencies and with fixed levels of cut and gain. You can boost and cut the same frequency at the same time. Frequencies from 200Hz to 3 kHz can be controlled in both the high and the low... Read more