This decoration originated around 1917, and is known on the 1917 Plainware line, the 3010 & 3020 Stemware lines and the 1630 Tumblers.
The D619 dates to 1917 and carried into the late 20s. The etch book shows two versions. One version (the top one) is so faded & misshapen that you cannot count the number of petals (all you can do is guess), while the second (the bottom one) has both a six petal and an eight petal flower within the treatment. So, there were two different treatments. Again, it's best that you look at the blank as well as the border treatment, tha'ts what dedicated Cambridge collectors do.