I was taking a closer look at my WW cover collection and rediscovered this cover from China scanned below.

The return address is Yenching University, Peiping, China, but the cancel on the stamp does not look like Peiping to me. I have yet to figure it out. Any ideas?
The interesting thing about this cover is that it was marked postage due 30 Centimes and arrived in Chicago 6 cents postage due. As you recall, I recently shared a Masons post card from Australia that was 30 Centimes postage due with 6 cents in postage due stamps applied. See this link...
https://goscf.com/t/82668I just find it interesting that this letter and that postcard were both assessed the same postage due. The China cover has precancelled postage due stamps marked Fort Morgan Colorado. No markings on the back of the cover, nothing at all to show. I am starting to get interested in WW postage due covers.
As always, comments welcomed.
Linus
