Blocks are colored, with significant wear, and are likely missing two windows, assuming the blocks match known examples. The pull-cord (two-hole, loop-style) is also missing.
The wheels have metal axles, and a blue pinwheel/spiral pattern.
Blocks present:
4 Oblongs (2 red, 1 green , 1 blue)
4 Squares (2 blue, 1 red, 1 green)
1 Doublong (green)
4 Diagonals (2 purple, 2 yellow)
2 Pillars (green)
2 Columns (yellow)
2 Panels (1 green, 1 orange)
1 Gothic Arch (green)
1 Half Circle (yellow)
I don't know yet where to put this chronologically. On first glance, I would put it right around 1940-1941, but the designs in those years are well known. Dating this to 1942-1945 for now, to match Holgate #354? 24 Junior Blocks in Wagon (incomplete), which has the same patterned wheels.
UPDATE: These wheels are on two wagons in the RS collection: one similar to Holgate #352 Wagon with 16 Colored Junior Blocks, and one similar to Holgate #550, Wagon of 50 Playroom Blocks (colored), putting it in the 1939-1942 range.
UPDATE 2: This wagon appears to be illustrated in a large advertisement in "The Kane Republican", on 5 December, 1940.