Show acquisition - Help me out!

 I need the expertise of some experienced collectors!  Help me out!

I grabbed this Dan Marino insert out of a dime box at a recent card show.  Didn't look too close, just saw a shiny Marino and threw a dime at it.  This pic is from my scanner:

1999 Upper Deck Black Diamond - Diamond Skills #S3

I got it home and was going through my various finds, and I noticed the imprinted markings on the middle of the card.  They are hard to see, right?  So I thought maybe it's a parallel, and went off to comc.com to look it up and see if I could figure it out.  No help at comc, all the copies on there had no imprinting.  

Now my eyes are getting pretty bad, so I broke out the old magnifying glass to see if I could figure out what the imprint says.

Here is another shot with a camera:

And a closeup:

And for those of you who still can't make it out (I can't!), here is some black text added in overlay:

And to show that is look s at least kind of professional, here is the back.  Whatever made the impression made a nice reverse image in the back of the card as well.

At this point, I am leaning toward this being some kind of promo or maybe a "do it yourself" prank.  The reasons I think that are:

1. I can't find any information on this anywhere.  Comc.com, TCDB.com, Google etc.

2. It was in a dime box

But it also kind of looks legit.  The imprinting, while hard to see, doesn't look like something that could easily be done at the quality level it has to an existing card.  Seems like something you would need good equipment do to.

So what do you think?  Anyone seen these before?