These lovely accessories were offered to the gaming world in the early 80's and I can't believe they didn't sell like hot cakes (However well hot cakes sell). Considering how many similar accessories there are on the market now, I would have imagined they would have been quite popular, but I never met anyone that used them or owned them.
Perhaps it was the nature of the game (1st edition AD&D) that didn't require these types of tool. Back then, all you needed was graph paper and imagination in equal parts. With then new systems, you are nearly required to use some sort of 1" scale mapping system, of which this is one. There are a ton of companies that seemingly took a note from these little beauties and are making some good quality products.
A further curiosity is the manufacturer's location: Pleasant Hill, Ca is within a few miles of me and I never knew they existed until about 30 minutes ago when I really looked at this ad.