From my private collection (husbands toy when he was young).  Red and green dump truck - Tonka Toys, Trade by Mark - Mound Metalcraft Inc, Mound, Minn.  It looks the same as a 1955 I saw and that would be the correct time frame but I am calling it 1950's since I am not certain of the year.  Tonka Toys are marked on each tire.  Made from metal.  Overall length is 13", 6" wide and 6" high (not in dump mode).  Looks pretty good for being 70 years old and played with by 3 little boys in the 1950's.   Feel free to make me an offer.