ricultural, labor, veterans, or fraternal organization or association. No permit is required.

(i) The following specific items when loaned or exchanged between schools, colleges, or universities, and public libraries, museums, and herbaria, nonprofit religious, educational, scientific, philanthropic, agricultural, labor, veterans, or fraternal organizations or associations; or when cooperatively processed by libraries; or loaned or exchanged between libraries, organizations, or associations, and their members, readers, or borrowers, may be mailed at the library rate:

(a) Books, consisting wholly of reading matter, scholarly bibliography, or reading matter with incidental blank spaces for notations and containing no advertising other than incidental announcements of books.

(b) Printed music, whether in bound form or in sheet form.

(c) Bound volumes of academic theses in typewritten or duplicated form.

(d) Periodicals, whether bound or unbound.

(e) Sound recordings. (See also subparagraph (5) (ii) (b).)

(f) Other library materials in printed, duplicated, or photographic form or in the form of unpublished manuscripts.

(g) Museum materials, specimens, collections, teaching aids, printed matter, and interpretative materials intended to inform and to further the educational work and interests of museums and herbaria.

(ii) The following specific items when sent to or from schools, colleges, universities, public libraries, museums, and herbaria and to or from nonprofit religious, educational, scientific, philanthropic, agricultural, labor, veterans, or fraternal organizations or associations, may be mailed at the library rate:

(a) 16-millimeter or narrower width films; filmstrips; transparencies; slides; microfilms; all of which must be positive prints in final form for viewing.

(b) Sound recordings.

(c) Museum materials, specimens, collections, teaching aids, printed matter, and interpretative materials intended to inform and to further the educational work and interests of museums and herbaria.

(d) Scientific or mathematical kits, instruments, or other devices.

(e) Catalogs of the materials in paragraphs (5) (ii) (a), (b), (c), and (d) having 24 or more pages, at least 22 of which are printed, and guides or scripts prepared solely for use with such materials.

(6) The address and each piece mailed at the rates provided by § 135.1 (c) and (d) must include the complete ZIP Code. When 5,000 or more identical pieces are mailed at these rates during a single day and there are enough pieces for the same destination to fill approximately onethird of a sack, they must be presorted and placed in sacks under the instructions contained in § 134.4 (c) of this chapter as follows: Subparagraph (2); and subdivisions (i)(b), (ii) (b), (iii) (b), (iv) (b), and (v) (b) of subparagraph (6). When 1,000 or more but less than 5,000 identical pieces are mailed at these rates during a single day and there are enough pieces for the same destination to fill approximately one-third of a sack, they must be presorted and placed in sacks under the instructions in § 134.4(c) of this chapter as follows: Subparagraph (2); and subdivisions (ii) (b), (iii) (b), (iv) (d), and (v) (b) of subparagraph (6).

(b) Application of rates. (1) The rates in § 135.1 (a) and (b) are applied on the basis of weight of the individual piece and the zone between the sectional center facilities of the post offices of mailing and delivery. Articles addressed to military post offices overseas (Army, Air Force, Fleet post offices, and Naval vessels) require postage at the zone rate applicable between mailing office and post office shown in the address.

(2) There is a local zone which is defined by the Postmaster General from time to time and eight numbered zones which are determined as follows:

(i) The United States and its territories and possessions are divided into units of area 30 minutes square, identical with a quarter of the area formed by the intersecting parallels of latitude and meridians of longitude. Each unit of area is designated by a number.

(ii) The zones are based on a straight line distance between the unit of area in which the dispatching sectional center of the mailing post office is located and the unit of area in which the receiving sectional center facility of the post office of address is located, measured from the center of one unit to the nearest point in the other.

(iii) An official zone chart prepared for each sectional center will be used to determine zones from all postal units within the sectional center area. The chart to be used is identified by the inclusive ZIP Codes assigned to postal units in the sectional center. Each chart lists the first three digits (prefix) of the Zip Codes of all sectional center offices and to the right thereof the applicable zone.

(iv) To determine the zone distance from the office of mailing to the office of address, refer to the zone chart for use at the office of mailing and locate on the chart the first three digits (prefix) of the ZIP Code of the post office of address. To the right thereof appears the zone.

(v) An official zone chart may be obtained free by request to the postmaster at the office of mailing. For ZIP Code numbers, consult the National ZIP Code Directory.

(3) The rates in § 135.1 (c) and (d) are computed on the basis of the weight of the piece regardless of the zone to which addressed.

(4) The local rate in § 135.1 (a) and (b) applies to parcels mailed at any post office for local delivery at that office; at any city letter-carrier office or at any point within its delivery limits for delivery by carriers from that office; at any

office from which a rural route starts for delivery on the same route; and on a rural route for delivery at the office from which the route starts or on any rural route starting from that office.

(5) The zone 1 rate in § 135.1 (a) and (b) applies to parcels mailed between two post offices in the same sectional center area.

(6) Gold coin, gold bullion, and gold dust, between any two points in Alaska, or between any point in Alaska and any point in the other States or U.S. possessions are charged the rate in § 135.1(a). The gold must be enclosed in sealed packages not exceeding 50 pounds in weight and sent by registered mail.

§ 135.3 Weight and size limits.

(a) Conditions for determining limits.

(1) Between first-class post offices:

Effective July 1, 1971..

(2) All other parcels:

Parcels mailed at or to:

(3) Add both measurements.

§ 135.4 Payment of postage.

Mailers of fourth-class articles may use any method of paying postage. § 135.5 Enclosures and additions.

(a) Required—(1) Return address. The return address of the sender must be shown on all fourth-class mail. See § 135.2(a) (5) concerning packages mailed at the library rate.

(2) Special markings. See §§ 121.6, 135.1(b) (1) (i), 135.2(a) (5), and 138.3 of this chapter for special markings required.

(3) Customs declarations. See §§ 124.8 (d) and 126.2 concerning need for customs declaration forms for packages addressed to the Canal Zone and to certain military post offices overseas.

(b) Permissible. (1) The following written additions may be placed on the wrapper, on a tag or label attached to the outside of the parcel (see § 123.2(b) for space requirements), or inside the parcel, either attached to an article or loose:

(i) Marks, numbers, name, or letters descriptive of contents.

(ii) "Please do not open until Christmas," "Merry Christmas," "Mom and Dad," "Happy Birthday," "Mother," "With Best Wishes," "John Doe," and similar inscriptions.

(iii) Instructions and directions for the use of an article in the package. Example: Directions for use of prescription medicine.

(iv) Manuscript dedication or inscription not in the nature of personal correspondence.

(v) Marks to call attention to any word or passage in text.

1

(vi) Corrections of typographical errors in

(a) Circulars or printed matter. Handwritten or typewritten changes or additions in the body of a circular are limited to corrections of actual typographical errors:

(b) Proof sheets. Corrections in proof sheets include corrections of typograph

ical and other errors, alterations of text, insertion of new text, marginal instructions to the printer, and rewrites of parts if necessary for correction. Corrections should be on margins or attached to the manuscript. Do not enclose manuscript of another article.

(vii) Handstamped imprints, except when the added matter is in itself personal or converts the original matter to a personal communication.

(viii) Any printed matter mailable as third class.

(2) An invoice whether or not also serving as a bill relating solely to the matter with which it is enclosed, may be enclosed or placed in an envelope (marked Invoice Enclosed) attached to the outside, showing any or all of the following:

(i) Names and addresses of sender and addressee.

(ii) Names and quantities of articles enclosed.

(iii) Description of articles enclosed, including price, tax, style, stock number, size, and quality; and if defective, nature of defect.

(iv) Order or file number, date of order, date and manner of shipment, shipping weight, and postage paid. (v) Initials or name of packer or checker.

§ 135.6

Enclosures with items mailed at catalog, special fourth-class, and library rate.

(a) Catalogs and similar printed advertising matter in bound form. The following may be enclosed loose or attached in items mailed at the postage rates shown in § 135.1(b) (1) and (3).

(1) Order forms, reply envelopes and cards, circulars, and miscellaneous types of printed advertising sheets.

(2) An invoice as provided for by § 135.5 (b) (2).

Samples of merchandise may be attached to the bound pages and to the loose enclosures.

(b) Special fourth-class and library rate (1) Books. The following may be enclosed with books:

(i) Incidental announcements of books, appearing in book pages or as loose enclosures. This includes an addressed envelope or post card, a single

order form, and a printed circular, each of which must relate exclusively to books. (ii) An invoice. (See § 135.5 (b) (2).) (2) Sound recordings. The following may be enclosed with sou..d recordings mailed at the rates in § 135.1(c).

(i) Incidental announcements of sound recordings appearing on title labels, on protective sleeves, on the carton or wrapper, or in the form of loose enclosures.

(ii) Guides or scripts prepared solely use with such recordings.

(iii) An invoice. (See § 135.5 (b) (2).) (3) All other items listed in § 135.2 (a) (4) and (5). Enclosures are not permitted except as provided in § 135.5 (b) (2).