We find many numbers on the the Truth Entrygard Dyad window operators. Numbers like 30636, 30637, 31367, 20544 and 20810. These numbers are helpful, but do not tell us what you have, they just narrow it down so we can make an educated guess as to what you have. In the last 15-20 years this operator has been redesigned. The arm coming out of the mechanism is now a diamond shape, it used to be a "S" shaped arm. My guess is they changed the shape of the arm because the "S" shaped arm would buckle. Below is a diagram of the older "S" shaped arm in the operator.
We usually find 20810A or 20544 stamped on the linkage arm. We offer two versions of this operator, both have a 4" long, linkage arm, the only difference is the the offset, either up or down.