Herbert Hoover (1874-1964) was the 31st President of the United States. He was in office from 1929 - 1933 during the Great Depression. The letter you mention being dated November 15, 1928 would be after he won the election in November and prior to him being sworn in as President of the United States in January 1929. As there is not an image of the letter showing here, these dates presume the letter is not a Presidential letterhead, but private stationary instead. The assumption is also that this is a typewriter written and hand signed letter. The estimate is based on actual past auction sales of comparables. Retail prices may be higher and vary.