These stamps were printed at the beginning of the war, after the normal Chung Hwa Printing were done. The Chung Hwa printing of 1939 were printed without watermark (Perf 12½) in either Die 1, 2 or 3. These were printed in 1941 (Perf 12½) on WATERMARKED paper (Wmk was the character yu.) The button on the collar of SYS is perfect in the first first row and progresses to a half or "imperfect" button in the last four rows. They are listed as 376-380 in the Scott catalog without any distinction between the "perfect" full button and the "imperfect" half button. The China stamp society has separate listings for the perfect and imperfect buttons. The full sheet has the advantage of showing the progression of the change in printing from perfect to imperfect. The top frames are fully shaded on all stamps. (Be careful of the Dah Tung printing with Watermark which is perforation 14).