Most specimens and equivalent markings were applied by the printer. The main exceptions are items overprinted or surcharged locally.
The types of protective markings used in any one country or postal territory are described and illustrated below the list of items distributed by the UPU. Where markings have been attributed to a particular printer they are also detailed below.
Dimensions are usually given to the nearest ½ mm. It should be noted that measurements can vary by up to at least 1 mm in length and ½ mm in height. In some instances more than one very similar overprint cliché was used or the overprint was set (and reset) in a forme from loose type over a period. Furthermore, by the very nature of the material overprinted the size of the impression may vary. There is also the difficulty that different individuals will record different measurements for identical items, sometimes as a result of excluding the serif on the first or last letter.
The majority of items were printed by the foremost London security printers: Bradbury, Wilkinson; De La Rue (by far the most numerous); Harrison & Sons; ???Perkins, Bacon; Waterlow & Co.; and McCorquodale (registered envelopes only).
Exceptions include the Australian States, Australia, Canada, New Zealand, and ???South (and South West) Africa. In these cases postal stationery was printed locally.
For postal stationery of Great Britain overprinted for use in certain British Colonies and Protectorates the protective overprinting was carried out by the Inland Revenue or the General Post Office.
The registered envelopes printed by McCorquodale were produced under sub-contract from De La Rue ???or one of the other security printers and the protective markings were applied by the main contractors.
The type numbers shown in curly brackets are tentative and may be changed in
due course.
The ranges of dates used are likely to be extended.
| type | dates used | image | dimensions | application |
| B{3} | 1914 | |
31 × 4 | overprinted diag BL to TR |
| B{7} | 1937 | |
50 × 6 | overprinted diag BL to TR |
| B{8} | 1937 | |
82 × 9 | overprinted diag BL to TR |
| B{10} | 1938-51 | |
75 × 8 | overprinted diag BL to TR |
| B{14} | 1951 | |
73 × 10½ | overprinted diag TL to BR |
| type | dates used | image | dimensions | application |
| D{2} | 1886–89 |  |
89– 90 × 8½–9 | overprinted diag BL to TR |
| D{2a} | 1889–92 | as above | 89– 90 × 8½–9 | overprinted diag TL to BR |
| D{4} | 1894–1928 |  |
91½–93 × 8½–9 | overprinted diag BL to TR |
| D{4a} | 1898 | as above | 91½–93 × 8½–9 | overprinted diag TL to BR |
| D{4r} | 1901–28 | as above | 91½–93 × 8½–9 | overprinted diag BR to TL (inverted) on reverse |
| D{4ra} | as above | 91½–93 × 8½–9 | overprinted diag TL to BR on reverse | |
| D{4rb} |
as above | 91½–93 × 8½–9 | overprinted diag TR to BL (inverted) on reverse | |
| D{4rc} |
as above | 91½–93 × 8½–9 | overprinted diag BL to TR on reverse | |
| D{6} | 1925 |  |
85 × 9½ | overprinted diag BL to TR |
| D{7} | 1926–27 |  |
65 × 10 | overprinted diag BL to TR |
| D{7a} | as above | 65 × 10 | overprinted diag TL to BR | |
| D{8} | 1928–37 |  |
56½ × 7½ | overprinted diag BL to TR |
| D{8a} | 1932–35 | as above | 56½ × 7½ | overprinted diag TL to BR |
| D{9} | 1937–48 |  |
41 × 3½ | overprinted diag BL to TR |
| D{9a} | 1937–40 | as above | 41 × 3½ | overprinted diag TL to BR |
| D{12} | 1941 |  |
82½ × 4 | overprinted diag BL to TR |
| D{15} |
1942 |  |
42 × 4 | rubber h/s diag BL to TR in violet |
| D{18} | 1946 |  |
41½ × 5 | overprinted diag BL to TR |
Types D{2} and D{4}, and their sub-types, appear to have been printed from loose type set in a forme. In consequence, whenever the type was reset the length of the overprint varies.
During the period from 1901 to 1928, and possibly longer, type D{4} was printed on the reverse of registered envelopes when the stamp was printed on the flap and the flap was folded onto the back of the envelope.
There are four possible orientations of the overprint: D{4r}, D{4ra}, D{4rb} and D{4rc} illustrated below.
| type | dates used | image | dimensions | application |
| H{1} | 1927–29 |  |
65 × 7½ | overprinted diag BL to TR |
| H{2} | 1931 |  |
50 × 8 | overprinted diag BL to TR |
| H{3} | 1933–45 |  |
57 × 8 | overprinted diag BL to TR |
| H{4} | 1942–45 |  |
55 × 7½ | rubber h/s diag BL to TR in blackish purple |
| H{4a} | 1944 | as above | 55 × 7½ | rubber h/s diag BR to TL (inverted) in blackish purple |
| H{5} | 1948 |  |
71 × 8 | overprinted diag BL to TR |
| type | dates used | image | dimensions | application |
| W{1} | 1932–38 |  |
43 × 6 | overprinted diag BL to TR |
| W{4} | 1935–38 |  |
68 × 8½ |
overprinted diag BL to TR |
| W{6} | 1935–40 |  |
76 × 7½ |
overprinted diag BL to TR |
| W{8} | 1938–39 |  |
88 × 7 |
overprinted diag BL to TR |
| W{10} | 1939 |  |
41 × 5½ |
overprinted diag BL to TR |
| W{12} | 1944 |  |
85 × 9 |
overprinted diag BL to TR |
| W{15} | 1944 |  |
85 × 11 | overprinted diag BL to TR |
| W{18} | 1945 |  |
59 × 6 |
overprinted diag BL to TR |
| W{20} | 1952 |  |
46 × 5 |
overprinted diag BL to TR |
| type | dates used | image | dimensions | application |
| GB9 | 1890–93 |  |
14¾ × 2 | handstamped horiz on stamp |
| GB16 | 1906 |  |
15½ × 2¾ | handstamped horiz on stamp |
| GB17 | 1907 |  |
16 × 2¾ | printed on stamp |
Introduction page List of countries