Came across this kind of by accident when I was searching for something else:
http://www.boeing.com/commercial/airports/acaps/727sec3.pdf
On page 15 and 16, charts for the "-200 Standard and Advanced" you can see that on the chart it makes mention of "Flaps 20" with an irregular dashed line. On pages 17-22, charts for "-200 Advanced" you can see that the "Flaps 20" is in a solid line. "Flaps 20" lines do not exist on charts for "-100" or "-200 Standard only" showing that Flaps 20 was a purely 727-200/Adv. option.