Serial numbers really don't mean anything as people will think it's one brand when it is not. And some brands outsource certain clarinets of which the serial number then does not have any correlation to the primary brand name.
Most soprano clarinets are in Bb are about 26 inches long
A clarinets are a little longer than a Bb, so about 27-28 inches
and Eb are about 19 inches long
fyi, the length I'm going off the top of my head but I would have to measure some to get an exact measurement.
It would be best if you were able to see it in person and take pictures, or have a bunch of pictures sent to you. Pictures that include the serial number, each joint, the upper joint that include the main emblem and possibly the model number.
There are also fakes out there that look pretty good. If you were only given a serial number and cannot get anything more I would pass on that instrument.