Wow! Don't know for sure, but that looks like something from the end of the Balata era or the Professional era. Those had some sidestamps such as "Tour Balata A 90" (sorry, keyboard doesn't have a solid, equilateral triangle, so I used a cap A instead) or "Professional A 90". There really hasn't been a compression rating on Titleists since the introduction of the first Pro V1, when solid core and no elastic thread replaced the traditional wound ball (rubber encased, liquid center for balatas; don't recall what the centers were for Professionals and the subsequent Tour Prestige models).

I think if you do some research, the 90 and 100 compression values were due to some inconsistency of winding tension, thus finding a way to market the variable. I believe that another club manufacturer marketed their inconsistent clubhead lie angles as a means of providing fitting, a way to market the production variability of their cast clubheads, too. Creativity!

Thanks for the reply Thomas. I’m 100% sure it is wound as it has a small ‘egg’ on it where it has been hit with the edge of a blade. The groups of six larger dimples in a pentagon shape (with one in the middle) Are like no other I’ve ever seen on a Titleist and that font on the side stamp looks very similar to Maxfli around the Revolution era? I’m sure someone on here will have an answer! Steve

I have a not so wild theory... I think that this ball is a test Maxfli A10 balls from circa 2002. Suppose they could have tried to appeal to the Titleist punter by dressing it up like a Titleist! The Un-Titleist like font on the side kind of points to this too. The A10 was an amazing ball.