If there is a lot of "feathering" on the underside of those white ribbons (like someone dragged a fine fork through the underside of the white striping glass) on the inside of the marble, it might be CAC, but 3/4" would be a much less common size for CAC than Alley, and CAC didn't make anywhere near the numbers Alley made either, hence my hesitation to go there. Either way, the shape suggests it's probably dug.