The cube looked like this:
https://sites.google.com/site/minisatellites/cube/Cube.JPG
The letters were yellow, carved in the body of the cube using something thin like a needle and they were filled with some yellow material, possible wax.
The cube was well polished and there was no indication that it once had something on it, for instance a bust.
Note: I repeat, I do not remember the inscription exactly.
Somebody reading the text translated it quickly in:
"The Senate and the Roman People decided to make emperor Nerva Trajanus consul, for the seventh time." But again I do not remember the exact words, precisely.