2001 Donruss Class of 2001 Baseball Forum

I have 9 cards of Terrence Long number 73 sitting in front of me.  3 of them on the back have a mostly green coloring on the left side and the card no. sits inside a brownish oval.  The other 6 are mostly black or very dark green and its very hard to tell if the oval around the card number is actually there or not. No other obvious differences. I know that coloring of ink can vary sometimes due to human error but this seems odd since I have a handful of each. 

I looked thru the external links and don't see any references to a variation like this. I don't have many cards from this set so I don't see this in any other cards I have. Any thoughts?