All of the airmail essay and proof material show below comes from the collection of W. Curtis Livingston. Many of the items were previously in the collections of G. H. Davis and Bernard "Bud" Hennig. Other than the die proofs of C4-6 and C7-9 these essays and proofs are the only examples in private hands.

  C4-C6P1
Complete full size set of die proofs printed on india paper (except for the 8c value which is printed on wove paper) and die sunk on card. Each is signed by then Postmaster General Harry s. New. This set being one of the presentations sets prepared at News's direction and given to members of the Coolidge administration during their last weeks in office. There is a bureau control number on the back of each card: 154047 (8c), 123085 (16c), and 123348 (24c). A scarce set in beautiful condition. (Ex-Livingston) $12,000.00

  C7-C9P1
Complete set of full size die proofs printed on wove paper and die sunk on card. Each is signed by then Postmaster General Harry s. New. This set being one of the presentations sets prepared at News's direction and given to members of the Coolidge administration during their last weeks in office. There is a bureau control number on the back of each card: 1369980 (10c), 5787 (15c), and 31553 (20c) Ex-Livingston) $9,000.00

   C11
Large bi-color large die proof printed on wove paper and die sunk on full size card, and signed by Harry S. New, Postmaster General. Both Bureau control numbers are printed on the back (123474 & 123475). A rare pristine example. Ex-Livingston $7,500.00

  C33P1
Full size die proof printed on wove paper and die sunk on card which originally came from the estate of C.A. Brooks the vignette engraver.  The typical "C" punch has been taped back into place. Bureau handstamp on the back reads: "Engravers Stock Proof/Authorized By" and initialed with "Brooks". The Bureau control number on the back is: 914145A. (Ex-Hennig and Livingston)$5,000.00

   C44P1
Full size die proof printed on wove paper and die sunk on card which originally came from the estate of M. D. Fenton the vignette engraver.  The typical "C" punch has been taped back into place. Bureau handstamp on the back reads: "Engravers Stock Proof/Authorized By" and initialed with "Fenton". The Bureau control number on the back is: 986580A. (Ex-Livingston) $5,000.00

  C44P2
Small die proof printed on yellowish wove bond. An extremely rare proof which does not have the typical Bureau "C" punch. There is also a 1994 PF certificate. (Ex-Livingston) $2,750.00

 C45P1
Full size die proof printed on wove paper and die sunk on card which originally came from the estate of C.A. Brooks the vignette engraver.  The typical "C" punch has been taped back into place. Bureau handstamp on the back reads: "Engravers Stock Proof/Authorized By" and initialed with "Brooks". The Bureau control number on the back is: 988830A. (Ex-Hennig and Livingston)$5,000.00

  C45P2
Small die proof printed on yellowish wove bond. An extremely rare proof which does not have the typical Bureau "C" punch. The only known small die proof of this issue in public hands. There is also a 1994 PF certificate. (Ex-Livingston) $5,000.00

  C47P1
Full size die proof printed on wove paper and die sunk on card which probably came from the estate of M. D. Fenton the vignette engraver.  The typical "C" punch has been taped back into place. Bureau handstamp on the back reads: "Engravers Stock Proof/Authorized By".  The Bureau control number on the back is: 120359B. $5,000.00

  CE1-2 
Seal of the President of the United States die proof printed on india paper and mounted on card. A variant of this design was used for the central design for CE1 and 2 air post special delivery stamps. The Bureau control number on the back is: 751316. $750.00