1978 HiFi Stereo Buyers Guide, these were big money in 1978, $4.79 is a whopping $24.83 today! We always had specials in the USA, maybe 20% off but these were still very expensive.
These were huge when they came out, this is the first test I've seen from HiFi Stereo Buyer's Guide 1978. Adjusted for inflation it would be $113.99 USD today! It looks like these actually work, The "HD-01 works exceptionally well." I think I have a later version of this, with the cool clear case so you can see the electronics and I also have one from Geneva, they bought out Nortronics and kept the company going with audio accessories. Mine is dated 1986 and was $11.99 purchased from Best Buy.
From Philips 1968 Compact Cassette Catalog https://archive.org/details/philips-1968-tonbandgerte/page/n1/mode/1up
The 180 LN - i still looking for it. It was the precursor of the D-C180, here i have two, from 1972 and 1979. But i never used some.