This is a silver “Metal Gear Solid” branded Playstation 1 memory card, and was a pre-order bonus for anyone who bought the game from Woolworths. The card, produced by Joytech, did come in a CD style case with front and back inserts however I just have the card on its own.
This is not particular rare as about 25,000 were produced, however expect to pay about £5 for the card alone and over £10 if you can find one in its own case. I bought this off ebay for about £4 as a bit of an impulse buy. The overall condition is not too bad, however I would like a complete one with case at some point.