I always figured these balls were in the poolhall's set to replace stolen/lost cueballs. In my regular hangout, there's more than a few racks that have cueballs that are a tiny bit smaller (import knockoffs???) than the object balls and several more racks that have 8-balls that have a not-so-shiny finish to them. I think they are probably going the cheapest route whenever they are replacing stolen/lost balls.
Maniac (leaning heavily toward "stolen" as opposed to "lost")
I agree with this as well. In fact, there's only one pool hall near me that
doesn't have a mix of Centennials and Aramith balls in each tray of balls (they do their due diligence to keep the balls matched). It's odd when I go to a pool hall, getting a tray of balls, and some balls have the Centennial "darts" while others don't, and some stripe balls have the numbers on the white area of the balls while other stripe balls have the numbers in the stripe itself.
What will be interesting, though, is that these differences will probably vanish, as Aramith was already well on their way to "standardizing" all their ball product specifications
(i.e. weights, size tolerances, and resins -- making them all pretty much the same) before Aramith themselves was bought by Simonis. As corporate acquisitions normally go, the whale-doing-the-swallowing will want to further streamline the whale-being-swallowed's products. We may see a day when there won't be a difference between a Red Circle and Pro Cup (measles) ball, save for the markings on the ball.
-Sean