How old is this brick? How old would you say this brick is? It has the code 2837 on the inside of it. Any info would be appreciated.
It looks like part of the old 9-Volt motor that was made from 1990 and 2002.

The full thing's part number is listed as 2838 which I assume is the mold ID stamped on dark grey base, while 2837 is the mold ID of the top part.
I don't think it's supposed to come apart, it looks like there are 4 clips on each sides which have been broken off of your piece.