One can't get enough Steinberg's LTB USB MIDI interfaces.

Like the Midex-8, the Midex-3 is an EZ-USB design, with a Cypress_AN2131SC as the main USB/MCU component here.
No need for an extra UART to run only 1x3 I/O.
Similar design than the Midiman/M-Audio Midisport 2x2:
https://youtu.be/qOnSU3csuE4 Except for the firmware of course, which handle LTB when used with a compatible software sequencer.
To bad they didn't come up with a LED when LTB is activated. Emagic did not either with AMT.
The housing is just two Macrolon shells plugged together with a tad of glue, holding the electronic board tightly.
This one has a BEK factory sticker which numbers have nothing to do with the one on the registration card.
Nothing on the cardboard either, but Made in Germany.
Most likely built by BEK Systemtechnik, which happen to build products for Kemper Digital GmbH, Access Music mother company (and LTB developper):
https://www.bek-systemtechnik.de/en/products/references/The included DRIVERS_2_2002 CD-Rom is hybrid PC/MAC, but I only could get access to the PC files (about 224MB of various boring Steinberg stuff) .
Made a RAW image with CloneCD: it weights 474MB zipped, so there's definitely extra stuff included.
You can grab it
there.