This sure seems a curious item, but I don't have reason to believe that the seller is intentionally trying to be deceitful.
I looked at the image of the letter on the
ebay posting, and it does indeed appear to be dated "Feb 23rd 1813".
On closer examination of the penmanship, however, you can notice that the single stroke of the first digit in the year (the "1") is near vertical, but the single stroke of the third digit is not parallel to the first; instead, it is at a 30 degree angle and has a wide margin away from the top of the "8" to it's left.
It appears more likely that the third digit in the year is a "7" without a clear top bar, and that the date was intended to be written as "Feb 23rd 1873," which would be more consistent with an envelope with a postage stamp.
Nonetheless, I remain puzzled because if the letter were sent in 1873, wouldn't it be somewhat unusual to be franked with a possibly 10+ year old stamp, like Scott 65?
Wouldn't you more likely see an 1873 envelope franked with either Scott 88 or 94? But I don't see any evidence of a grill on the stamp as shown, so it must be Scott 65.
And another puzzle: the CDS reads "Three Oaks, Mich, Nov. 2". Why would a letter dated in February be in an envelope with a November CDS?
Just my thoughts (and more questions) on the subject.
Kevin