I received a sleeve of these <test> balls.  I loved the feel and spin as compared to my current ball.  So, to answer your question, they are prototypes that Titleist sent out for testing.

I also received a sleeve of these and could tell a difference in spin off of the driver. The biggest thing for me was the feel off of the putter. It is amazing.

I received a sleeve of the pro to ProV1X, as well - great ball. Similar to the previous model but slightly lower launching (closer to '09) and MUCH improved durability.

ya the prototype prov1x is very similar to the 09 model...anyone get the black #'s? how are they compared to the current prov1? 

I received the proto balls with the black numbers- ProV. The ball is a little softer and lower spinning off the driver. Little harder to turn the ball right to left with the driver.The ball feels awesome around the greens. Cant wait for the new ball to come out. 

 I normally play the V1X "Red" but through swapping with a buddy,  I tested both types of balls.   The new Pro V1 "Black" version had characteristics close to the 2011 "Red" ball.   The durability on both were outstanding.  I played a "Black" version for appoximately 72 holes and it was still in remarkable condition.  Hit many crisp Vokey wedges with it and didn't see the usually scraping effect.  All being said,  I will continue to play the "Red" ball in the new version,  but for me,  the difference is now very small between the two..... 

These are the new prov and provx probably coming out next year.

These are longer straighter, than my prox x's now.

SUPER BALL

GREAT FEEL GREAT TOUCH AND GREAT IN THE WIND.

Ya select team titleist members and staffers played these to test during the fall testing session. The purpose was just testing changes to the prov1 for 2013