How rare is the apple leather case for ipod?

I recently was searching for and bought a case that was apple branded for the ipod video. The product number is MA399G/A. It is for the 60gb/80gb ipod videos.

My main concern was, how rare are these cases. I had to search the product number to even find it and none have sold on eBay, other than the one I bought, in the last year or so. I had to get mine from the UK, as I'm I the US.

If anyone knows how rare these are, let me know. Thanks.