INSTRUCTIONAL MARKS & POSTAGE DUE: a trio of 1923-38 covers with v. fine hs inc. 1928 env. to London with a boxed LIABLE TO LETTER RATE / 15 and 2D hs, a 1923 underpaid PC with a 2D hs and P. Due stamp, and a 1938 Registered Letter env. to USA with a boxed POSTED OUT OF COURSE / 15 and 3D hs. Cross Reference : INSTRUCTIONAL MARKS, POSTAGE DUE STAMPS & COVERS (Image)