I believe it is the earliest sets of U.S Embossing Company Color Cubes that were made with with a raised edge for the diagonals, as is the case on these, dating to the 1930s I believe. This is a nice large set of 49, themselves in very good condition, with little paint loss (though the box has seen better days!) I'll never tire of playing with these, and think one can never have too many. The underside of the lid features many possible arrangements for inspiration if needed!
Cubes measure about 1 1/16" square; box about 8 1/4" x 8 1/4" x 1 1/2"