WM-550C

The WM-550C was a sound-oriented playback Walkman from 1988 built around Dolby B and C noise reduction, an EX Amorphous Head, Dynamic Bass Boost, and switchable auto-reverse inside a compact horizontal metal body. It supported normal, chrome, and metal tapes through a manual tape-type selector and could run from either an external AA attachment or an internal rechargeable gumstick setup. Everything about it was configured to make a relatively compact player sound and behave more seriously than the average midrange unit.

It shows Sony still taking portable cassette fidelity seriously even as the category matured. The 550C was not the flashiest object in the range, but it was clearly meant for listeners who cared more about lower noise, head quality, and playback refinement than styling experiments or unusual features. It reads as a player built for people who still wanted to believe the cassette itself had room left.