D&D Products of the 1970s and Sandbox Games
But what I see is a lot of products designed as resources for Dungeon Masters. You had your Monster & Treasure Assortments and Dungeon Geomorphs. Judges Guild produced a gazillion products with dungeon and wilderness maps, random encounters, etc.
As I'm prepping my first "real" sandbox style game I have to confess I see the utility in them. Not knowing precisely what the players will do has me going through my not inconsiderable gaming library (stretching, if not back to the 1970s, at least to the 80s - when a lot of those old products were still in print). Lots of adventures I've used in the past seem just perfect for location x or location y. Heck I can see the value in random encounters, something I don't think I've used in ages. Once you have an idea as to who lives in that mountain range, it is not unreasonable that characters adventuring in that area will run into those beasties. It draws to mind the adventure of Bilbo Baggins, whose encounter with trolls screams "random encounter".