1836 Express Mail

I have a stampless letter datelined December 7, 1836 at NYC. The cover is addressed to Baltimore and has a December 7 NYC CDS. The lower left corner has a written notation "Express Mail" and the upper right corner is written "Single." The cover has a manuscript 18 3/4 cents rate instead of the express mail triple rate of 56 1/4 cents for 150-400 miles. The "Express Mail" handwriting matches the rest of the cover. What gives? Did the sender change his mind? Thanks for any suggestions.

We'll never know for sure, but a change of heart is certainly conceivable given the high relative value of 56 cents in 1836. The sender might have found out about the high rate only when s/he arrived at the post office to dispatch the letter and was informed by the clerk. However, I would have expected the clerk to cross out "Express Mail." Are there any receiving marks or transit marks on the reverse? Scans of front and back would be nice.

Thanks very much for your helpful reply. There are no transit or receiving marks, docketing, etc.

One other possibility is that it is a well done fake. Matching ink color and handwriting is not overly difficult for someone with a bit of experience and an Express letter would be worth more than a regualar rate cover.

Or another benign explanation might be that the sender intended it to go Express but arrived too late for it to go by that method and instead let it go by regular mail.