I haven't seen any since the Southdown branding. Old castle was the company that sold it (or sold under the Old Castle label), but I've not been able to get any real info on it in years. Some regions apparently had some left over bags (Philly was one mentioned in specific), but when I asked some well known reefers from the area, they said they'd not seen any in years, and were looking. I think it is a myth now.
I never rinsed my Southdown. The smaller particle size was what I was looking for. The story I was told is that the sand is collected from the same place (roughly) as the branded reef sand. The difference was that the Old Castle sand was processed with equipment that was not specific to reefing (might also push rocks and concrete/sticks, etc.). No big deal, though. I had small sticks in mine, but nothing of consequence.
Good luck finding more. If you find some, you may want to frame it and put it on ebay:D.
