30th President. TLS "Calvin Coolidge" AS PRESIDENT, The White House, Washington stationery, December 13, 1926, Coolidge writes to "Honorable Ernest R. Ackerman, House of Representatives, Washington, D.C.", in full:

I have your letter of December 11, and want you to know how much I appreciate your kind words about the Message.

It always is helpful, as well as a pleasure, to have the observations of one so competent to express sound views.

The "Message" referred to was Coolidge's State of the Union address from December 7, 1926.  Ackerman was a Republican from New Jersey who served in the House from 1919-1931 and also a famous philatelist.