You are correct. When I posted my initial response, I qualified it by saying that I would have to check my catalog collection to verify the actual period of usage. I have since checked my catalog collection and find that the sandblasted stocks were last cataloged in 1976. The 1977 catalog shows all Model O pistols with checkered stocks.I think that the sandblasted walnut stocks were used until the later 1970s. My 1975 Colt Series 70S .38 Super had those stocks, but IIRC it wasn't long after that, that all of the pistols started appearing with the checkered walnut/gold medallion style.