These blue ones are hard to find, and I haven't seen one on Ebay recently from this era. According to a response from the Radio Flyer headquarters, this was made in 1972-73. They don't have production numbers, but the majority of wagons were definitely red- not the less made blue.
The model 100's were the next grade down from the model 18, the classic original. They made many different sizes for all types of customers, and this one has a slightly smaller bed and smaller diameter wheels. I brushed the loose rust off and wiped it all down. She's in original condition as found and clean to the touch. All wheels spin and the steering rotates as it should. One of the rear wheels wobbles but not loose. I will remove the handle to ship. If you want the wheels and axles removed to ship, I will do so upon request.