I've never found any published grit specs for older Carborundum-branded stones. I have a Carborundum 111 stone, in 5" x 2" x 3/4" size, that I found among some items of my Dad's after he passed away. No numbers for grit on the box; in fact, they only label it as 'Double Grit', not even specifying a 'coarse', 'medium' or 'fine' for either side. I haven't used the stone yet. But by appearance and feel in-hand, this stone seems on par with other such SiC stones from Norton (Economy stone), Sears and ACE Hardware. In other words, maybe ~ 120 or so on the coarse side, and something in the 280-320 range on the fine side. I'm basing those numbers on Norton's grit chart for their SiC stones (Crystolon, including the 'Economy' stone). Norton's the only brand I know of with published grit specs for stones like these. Just so happens, Norton's current parent company, Saint-Gobain, is also the current owner of the Carborundum brand products of today. Still hard to know for sure though, what the older Carborundum is, based on only looks or feel in-hand.