| Covers listed |
|
| 1916: | 1 January, 15 January, 1 February, 15 February, 1 March, April, May, June, July, August, September, October, November, December, |
| 1917: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1918: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1919: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1920: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1921: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1922: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1923: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1924: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1925: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1926: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1927: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1928: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1929: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1930: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1931: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1932: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1933: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1934: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1935: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1936: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1937: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1938: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1939: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1940: | January, February, March, April, May, June, July, August, September, October, November, December, |
| 1941: | January, February, |
