Can anyone read the date?
To me it looks like OCT 17 6 PM, 1912? The stamp fits, it's from 1912...
I would guess in the mid twenties. I don't think the Ford jokes were popular until later when everyone owned a Ford. The Washington stamp was still being issued in 1923, perhaps later.
I was going to originally roll with 1922, but the bottoms of the numbers in the post mark don't look similar, the first digit looks smaller at the bottom than the second. But you definitely have a point.
Jay, thanks for posting.
Ford "humor" before the Model T:
This is a depiction of an early 1906 K with the camel hump radiator, long hood and plow share fenders.
What looks like another 06 K Ford, with long hood, plow share fenders, hand brake and shift lever:
(Message edited by Rob on August 05, 2016)