1935 Cover - Special Delivery? Thoughts?

This cover traveled from Evanston IL to Sharon PA on December 24, 1935 (chicago cancel) and arrived December 25, 1935 (11am backside to Sharon, PA).
One day delivery - appears to be Special Delivery but the those stamps were not used? No airmail stamps used? And at the time the postage rate was 3 cents, air mail 6 cents and air mail special delivery 16 cents. How did it get there for only 10 cents?

Your cover is significantly trimmed along the right side (note the image of the back side).
There are remnants of a missing stamp at the very top right corner.

It is not marked airmail, so the surface postage would 3 cents and the special delivery fee is 10 cents. It is missing a 3 cent stamp.

It would have gone by rail for the majority of its journey. I think the black mark on the back is a close variant of this Sala(manca, NY) and Chi(cago) mark. Several similar devices were in use over the years.The western division running from Chicago to Marion, OH

Illustration from the Mobile Post Office Society's RPO catalog.

Thank you John. I knew the envelope was trimmed and not great shape. I did not see the markings of the missing stamp - good catch. Love your analysis and specially the cancellation from the railroad cancellation on the back. Appreciate your review.