There are four generations of USB-eLicensers. They are compatible with each other.
The first model introduced in April 2002 is 6.7 cm long. In 2003 it has been replaced by a 1.5 cm shorter variant that is equipped with a faster processor. The serial number of the 1st and 2nd generation USB-eLicensers is printed on a small label on the printed circuit board.

The four generations of USB-eLicensers in chronological order from left to right.
The third USB-eLicenser revision came out in mid 2008. It is technically identical, only the housing is slightly darker coloured.
Since mid 2015 the fourth generation is in production. With a length of 3.8 cm, this model is even more compact thus more solid.
When using a 1st generation USB-eLicenser, the graphical user interface of licensed software may feel less responsive. In this case, we recommend replacing the USB-eLicenser with the latest model. New USB-eLicensers are available from any Steinberg dealer and, of course, in our online shop.