I too received a sleeve of test balls and I played one yesterday, now and then comparing it with my usual ProV1.  I'll go out on a limb here and assume that the test ball is this year's ProV1! 

Mine felt very hard, and the cover wore out fast with some bunker practice. I would say dt solo. It was only 7 degrees when I got out to short game practice. The weather might had something to do with the hardness.

Hi Thomas and Stephen,
We sent White Box Prototype Test Golf Balls out to several Team Titleist Members months ago.  Assuming these are the ones you are referring to, they are Pro V1 (if black number) and Pro V1x (if red number).  They are actually the softest Pro V1 and Pro V1x we've made.

Thank you for your feedback.

Cheers,
Mitch D
Team Titleist Canada