I've found a new one today
Its name is YP-Z32 and it's very rare
It has been released in 1999/2000 in 2 versions probably: one with 32Mb embedded memory (extensible up to 64Mb) with a serial port and another with 64Mb memory and USB 1.1 connection.
Here is the use manual: http://downloadcenter.samsung.com/content/...7437_YP-Z32.pdf
Description by a website that sold it at the time:
Wearable & pendant Style
Samsung's tiny, wearable Mini yepp is the world's smallest full-featured digital player, weighing in at a mere 1.13 ounces without battery. It comes with 64 MB of built-in flash memory and features an LCD display that shows music info and current date and time.
The Mini-Yepp has superb sound with a four-preset graphic equalizer and a powerful bass boost system that can enhance any musical style. The Mini-Yepp also features an advanced USB port for high-speed transfer of your favorite music. USB connections are three to five times faster than those using the parallel port, and they allow compatibility with both the Apple Macintosh and PCs running Windows 98, 2000, or Me.
The popular Rio-Port digital music software is bundled with the Mini-Yepp, offering a powerful yet easy-to-use system to organize your entire music collection and quickly transfer custom track combinations. The software is also CDDB-enabled, automatically retrieving artist and track information for millions of CDs (when connected to the Internet).
mp3 files playback
32/64MB Embedded Flash Memory
USB Data Transfer
4 Mode Equalizer
Real Time Clock
Format MP3 Music= Files Playback
Memory 32/64MB Flash Memory Embedded
Interface USB (Ver. 1.1)
Noise Ratio 90dB
Earphones Output Power 5mW
Output Frequency Range 20Hz~20kHz
Dimensions 42 x 70 x 22.1mm
Weight 32g (without Battery)
Battery 1 AAA / Lasting 4 hours (Alkaline Battery)