Darkhorse SR1 Normandy Model Key

I got a code with my SR1 Normandy Model from Forbidden Planet and I activated the code and I'm not exactly sure what the code does in ME3. The card says "For access to bonus multiplayer items" and I saw no additional items there. Anyone got any info on what these items are or what this key really gives me? The card says "Expires April 30, 2014" but the key said it activated succesfully. Has the key just expired and not given me anything or?