Duratone was first produced in October of 1960. The backstamp supports this date since it boasts the ware as, "DISHWASHER-PROOF." In general, there aren't very many lines prior to 1960 which make reference to dinnerware being dishwasher safe.
The name Duratone has two meanings. First the "Dura" part refers to its durability. Not only was this ware advertised as dishwasher-proof, but many vintage ads claim Duratone is, "guaranteed oven-proof, detergent proof and stain-resistant. It will not fade, craze or crackle." The "tone" is obvious from the treatments. Each has decal and trim that work together to produce a dominant color or tone. There were only about a dozen or so patterns offered on Duratone. A gray line called, "Charm Pattern" was sold though Montgomery Wards. Spring Garden is the only Duratone treatment where the its name is included in the backstamp. All others will have the same marking, but without the decoration name.
Flatware is made up of the generic coupe shapes derived from Rhythm and used on multiple lines, but the hollowware is unique. The sugar, creamer, sauceboat and casserole was modeled especially for this line. The shakers were borrowed from Jubilee and the generic shape jumbo salad bowl was also offered with some Duratone patterns.
Expect the larger plates and platters to be marked while smaller pieces may or may not have a backstamp. Hollowware is never found marked which became common practice starting in the very late 1950s and into the 1980s.