This type of crown you describe was called a unicrown, and was an intermediate step in the process of eliminating fixtures and manufacturing steps in the construction of a bicycle frame. The fork crown was eliminated, but the design never truly achieved it's goal of eliminating a manufacturing step like tig welding did because the fork blades still had to be formed into a curve or radius at the intersection of the steerer tube and blade to be mitered and welded to the crown, ergo adding a step in the process. It may have been a smidgin lighter than a fork with a crown, but not much. The design was used and still is used on steel forks of all levels of quality, from cheapest to highest quality. Here is an example of the same fork design on a top of the line Bianchi that is a replica of the bike Gianni Bugno used.