Envelopes, wrappers and labels

Envelopes are divided into two main styles—‘Banker’ envelopes, and ‘Pocket’ envelopes. The standard sizes of official envelopes are:

With the introduction of the new international standard sizes the banker shape envelopes listed above will in time be replaced by the new standard sizes C7 (3¼″ × 4½″), C6 (4½″ × 6½″) and C5/6 (4¼″ × 8⅝″). The measurements of an envelope are quoted in relation to the opening. Thus in this table of envelope sizes the dimension from the top edge of the flap to the bottom of the envelope is given first, i.e. depth × width. The sizes and terms used to describe commercial envelopes are given in British Standard 917:1949. Manufacturers’ machinery precludes the possibility of an exact standard and variations of ±⅛″ may occur from standard size between one manufacturer and another.

Ordinary ‘stock’ envelopes should be utilised on all possible occasions; every effort should be made to avoid demanding envelopes which bear special printings, or which are of special sizes. In particular, when substantial quantities of envelopes will be used, e.g. for large scale forms issue, standard sizes should be specified where possible so as to utilise to the utmost the high speed production facilities available. Where special supplies are essential several patterns of each kind should be forwarded with the demand, together with an explanation as to the necessity for departure from the standard sizes.

The smallest practicable size of envelope should be used, having regard to the time, cost and method of folding the enclosure, and to the fact that envelopes larger than 9″ × 4″ have to be date stamped by hand and sorted separately by the Post Office. Large covers are inconvenient to handle in the post and covers larger than foolscap size (3⅝″ × 8½″) should be used sparingly.

For details of quality in the various stock sizes, e.g. Buff, Thick Buff, Glazed Brown, Kraft, waxed paper under flap, and printing see H.M. Stationery Office List of Paper and Office Requisites held in stock for use in the Public Service.

There are two main kinds of cut out panel envelopes which reduce addressing work by making use of the address shown on the document inside the envelope, and which also eliminate the possibility of putting an enclosure in the wrong envelope:

1. ‘Window’ envelopes with a transparent panel.
2. ‘Aperture’ envelopes with an open cut out panel; this kind is inadmissible in the international service.

When window or aperture envelopes are used the enclosure has to be folded with care to make sure that the address is visible. If it is to remain visible it is necessary to fold so that the depth of the folded form is approximately equal to the depth of the envelope. Before using this type of envelope it is desirable to make a thorough test because the extra care required in folding and enveloping can offset the saving in time over the use of a pre-addressed envelope.

The use of the window envelopes with a transparent panel should be restricted to cases where privacy of the contents is essential. Window envelopes can be re-used with economy labels. Aperture envelopes are not normally re-usable. The range of sizes of these types of envelopes is limited and H.M. Stationery Office should be consulted about availability in the early stages of designing the form as an enclosure. Aperture envelopes for use with payable orders are stocked by H.M. Stationery Office (size 3⅛″ × 5⅜″ A/cs. Gen. 15a).

All correspondence must be made up to Post Office requirements about addresses, size, weight, colour and printing etc. Particular care should be taken to observe the special restrictions applied by the Post Office to window and aperture envelopes set out in the current edition of the Post Office Guide, and Post Office Leaflet P.2351.H. from which the following details are taken.

A packet enclosed in a window envelope must conform to the following conditions:

1. The panel must extend parallel to the length of the envelope.
2. A space of 1½ inches must be left above the panel for the postage stamp and the date-stamp impression.
3. No writing or printing other than the address may be displayed through the panel and the address must appear through the panel in such a manner as to be read with reasonable facility.
4. The enclosures must be so folded that they cannot move about in the envelope, and thus cause the address to be hidden.

A packet enclosed in an ‘aperture’ envelope (an envelope with an open panel) must conform to the following conditions:

1. The open (cut-out) panel must not exceed 3¾″ in length by 1¼″ in width.
2. The requirements shown in (1), (2), (3), (4), in the preceding paragraph concerning transparent panels.
3. A minimum space of at least half an inch must be left within the sides and base of the cut-out panel and the respective edges of the envelopes.

Entirely transparent envelopes, and envelopes likely to ‘trap’ other postal items are forbidden.

Envelopes in the form of continous stationery can be obtained for use with machines fitted with sprocket feed attachments.

Economy labels of the following sizes are stocked by H.M. Stationery Office:

* These larger sizes may be used as wrappers for circulars and correspondence of a non-permanent character without the use of envelopes. It may sometimes be necessary to consider certain features of mail handling equipment:

1. Envelope opening machines: the size of the document and envelope should permit the contents of the envelope to be shaken down below the depth of the cutting edge, to avoid mutilation of the contents.

An alternative is a two-way folder to convey typing work to and from the customers, and to provide all the details required by the typing staff. The address of the customer and typing pool need be written once only during the life of the folder. Where several typing pools or customer branches are involved, a different coloured folder could be used for each one. Punched holes to indicate when empty would add to the usefulness of this internal transit document

2. Folding machines: these machines can make a variety of folds, ranging from the single-fold to the more complicated accordion folds. Folding is so accurate that it facilitates the tuck-in of documents designed as postal folders, or the correct placing of the address when the document is despatched in a window envelope. A range of paper sizes, normally up to 12″ × 19″, can be passed through the machine.

3. Wrapping machines for magazines, catalogues and periodicals up to about 14″ × 12″ which can be rolled in wrappers up to 12″ × 14″.

4. Envelope inserting and sealing machines which can take document sizes from 4″ × 4″ to 84″ × 13″ and envelopes up to 9″ × 4″.

This window envelope is designed with a front flap on which the ‘ Official Paid’ design is printed in addition to being printed in the normal position on the front of the envelope itself. The flap is tucked inside to send out the blank form; when completed the form is confidential and is returned by sealing the gummed flap on the outside. After this ‘two way’ use the envelope can be further used with an economy label.