CC: Barely Perceptibly Different

2008 Topps Stadium Club #10 Proof

Okay, so I came across a copy of this card for sale, and although it looked pretty familiar, the price was low, so I went for it.  The thing is, I already had a 2008 TSC proof card.
In any case, let's examine what we have here.
First of all, let's compare this new card to the standard base issue.

 As you can see above, the proof card (left) is noticeably larger than the regular base card.  Other than that there's no difference.
Let's do another comparison, this time with a different proof card I purchased around the time Stadium Club was released (my God, twelve years ago, we're all going to die soon).

From left to right, my new proof card, the old proof card, and the regular base card.
The old proof stands out from the lack of foil printing, very normal for scavenged proof cards such as these.  It also stands a little bit taller than the newly acquired proof.  So what's going on here?  If we assume we're dealing with a genuine sample (and not someone engaging in what would be a money-losing effort to painstakingly fake these cards), then it stands to reason that proof cards can vary in size and degrees of completion, just like we see here.  Maybe the text-less card is an example from earlier in the process than the one with the foil.  In any case, it's a welcome addition to the collection.