Radio Shack had some Realistic speakers with that type of grill, for example, 1978's MC -1500 (it is a 2-way, though) and the 1975 Optimus 9 (5 drivers). The RS grills have different sized squares than you have pictured. RS sold the grill foam like your pictured grilles. I am not aware of any RS speakers with 3 drivers and that type of grill.
http://www.radioshackcatalogs.com/catalog_directory.html
The JBL L100 came with a grill very similar to that pictured, but that speaker is not a JBL L100.