Cam 30 Nov. 1928

This ones cool

Some background on that CAM-30 flight may be found here:

http://www.aerodacious.com/ccCAM030.HTM

It seems to be catalog number CAM 30S2 from Champaign to Evensville given the postmark and the offset ink from the backstamp of the cover that was on top of it when the ink was still wet. That makes the handwritten direction in the upper left corner incorrect as Chicago dispatches and Champaign dispatches were two different ones. Also, the Aerodacious website listing link provided by wt1 is a bit off on the value. The new Ameriacn Air Mail Catalog, Volume 1 of the 7th edition, assigns the value of this leg at $4 for one with the violet cachet as yours has, and $20 if you had one with the cachet stamped in black ink. There were 75 pounds of mail flown on this leg, which is a relatively large amount. The pilot was Charles H.Shield, Jr.