WM-3500SP

The WM-3500SP is a transparent-bodied variation of Sony's child-oriented WM-3500 cassette player, using the same basic controls and durable My First Sony construction while exposing the internal mechanism through a fully see-through shell. It kept the same simple playback-only function and battery-powered portability, but turned the object itself into part of the entertainment by making tape motion and internal parts visible in use.

This is exactly the kind of variant Sony handled unusually well. The WM-3500SP takes a simple children's cassette player and makes it much more memorable through presentation alone. It feels educational, playful, and slightly toy-like without losing the identity of a real working tape machine.