Those are mill balls. They feel like lead weights, and are cold to the touch. I believe this is the 3rd deceptive "paint job" scam on what has to be a MASSIVE amount of undesirable plain orbs.
The 1st time I saw these in the early 90's, people claimed they were dug out of Atlanta during the construction of the Olympic stadium there. They were mainly a variety of solid colors with a white star on them (coughBS...CoughBS)
The 2nd "run" was the Tennessee "dredge" marbles. You remember, the ones that were dredged out of the river? They all had floral patterns or some scene on them, with lots of patina crackle lines. Also felt like heavy lead balls, cold to the touch, and the exact same size.
Now these.... I think they popped up about a year ago. They called that paint jog the "Gutta Percha" marbles. Once again, heavy and cold to the touch.
Who ever has a wholesale contract with Sherman-Williams and an acre of mill balls, must be raking it in on the unknowing and new collectors.
Willie