Low end set. Table sellers would include the set with the purchase of a home table. I've come across many of these sets when giving pool lessons to people on their home tables. They play lighter than regulation balls and I think may even be a little smaller in size. Yes, the cue ball that came with the set had no markings on it. Not sure of the exact time frame. Definitely 80s and likely into the 90s. Later, Aramith produced their pro line to distinguish them from the cheaper sets.
Some pool rooms would use them and give them to the social players and save the Brunswick Centennials or the Aramith Pros for their regular players.