Somewhere on the back (or inside battery compartment on some handhelds) there should be a small black decal with white letters, which is the date code. My Pro-83 is silver with black letters.
It should look something like 09A05 ....
First two digits being the month 09 = September
Last two digits beint the year 05=2005
Really don't know what the letter is for....maybe A=1st series and B would be an updated model (just speculatoin on my part)
09A05 is the build date for all the bad 2055s wih faulty displays