The U.S. Postal Service will honor two Nobel Prize winners during the coming week: John Steinbeck, who was awarded the Nobel Prize for Literature in 1962, will be featured on a blue 15-cent adhesive to be released on Tuesday; and on March 4, Albert Einstein, who received the Nobel Prize for Physics in 1921, will be honored on another 15-cent commemorative. Both stamps were printed by the intaglio process and have identical image areas --.84 x 1.44 inches or 21.3 x 36.57 millimeters. Bradbury Thompson designed the two vertical stamps based on photographs.

The deadline for ordering first-day covers of the International Year of the Child stamps has been extended to March 31. Collectors preparing their own covers should send them to "First-Day Cancellations, Postmaster, Philadelphia, PA 19104." Those wishing the Postal Service to affix stamps should send covers and 15-cents per stamp to ""International Year of the Child Stamp, Postmaster, Philadelphia, PA 19104."

The deadline for submitting orders for the 10-cent multicolor George Rogers Clark postal card, which was issued on Friday, is March 10. Requests for firstday cancellations should be addressed to "George Rogers Clark, Postmaster, Vincennes, IN 47591."

Postal Service may well have erred in its choice of the depiction of George Rogers Clark's trek to Fort Sackville. Historians who have viewed the design have expressed some doubts as to whether Clark's frontiersmen would have actually bothered to carry an American flag along with them on their strenuous winter march. And, if indeed they had, there are still questions about the exact version of the fledgling nation's banner that they would have used. The general feeling is that if Clark's group carried any flag at all, it would have been a green regimental standard.

The volume of mail handled by the U.S. Postal Service rose 5.1 percent during 1978, a gain of over 4.7 billion pieces, according to Postmaster General William F. Bolger's annual report to the Postal Service's Board of Governors. The largest gain was in third-class mail, with an increase of 9.5 percent. First-class mail, which represents about 58 percent of USPS's total volume, also rose by 4.3 percent. Some of the increase in first-class mail was attributed to the presort system. In 1977, the first full year for presort service, first-class presorted mail volume was 2.2 billion. In 1978, it climbed to 3.3 billion. The only mail category which declined in volume was fourth-class mail, which fell 9.3 percent over last year. Perhaps the best news included in the report, is that, barring any unforeseen difficulties, the Postal Service may finish fiscal year 1979 with a surplus of $180 million.

John E. Fox Jr., president of the American Philatelic Society, has announced that in the future, the John N. Luff Award -- the APS's highest honor -- will be given annually, rather than biennially, which has been the practice since its inception in 1940. The Luff awards are for "meritorious contributions to philately by living philatelists" and are presented in three categories: for distinguished philatelic research; for exceptional contributions to philately; and for outstanding service to the American Philatelic Society. Nominations will close on March 30. Anyone may send in nominations. A biographical sketch of up to 300 words, outlining the candidates qualifications, is required. According to the society, nominees need not be a member of the APS. Nominations should be sent to Mr. David Lidman, P.O. Box 567, Southbury, CT 06488.

In the area of foreign new issues, four Swiss portrait stamps were released on Feb. 21. The stamps are the last of a series featuring famous writers and painters who have made Switzerland their home. Included in the issue are Rainer Maria Rilke (20 centimes), Paul Klee (40 centimes), Hermann Hesse (70 centimes), and Thomas Mann (80 centimes). Graphic artist Hans Erni designed the stamps.

Among foreign issues scheduled to appear this week are a se-tenant strip of five from the Seychelles and four adhesives from the Isle of Man. Birds indigenous to the Seychelles are featured on that country's set, to be released on Tuesday. The lithographed stamps include the Seychelles Fody, Green-backed Heron, Seychelles Bulbul, Seychelles Cave Swiftlet, and the Grey-Headed Lovebird. The Isle of Man issues, also scheduled for release on Tuesday, feature the Isle's Natural History and Antiquarian Society. Values of this lithographed set include 6, 7, 11 and 13 pence.

COINS

The introduction of the Susan B. Anthony mini-dollar on July 31 will mark the first significant reduction in the size of a circulating denomination since the minting of the Flying Eagle cents 122 years ago. The Flying Eagles replaced the hefty and more cumbersome Large Cents, minted between 1793 and 1857. The smaller cents weighed approximately 59 percent less and greatly reduced minting costs. It ushered in a shift in the basic composition of one-cent pieces from all copper to 12 percent nickel and 88 percent copper. The nickel was added in the hopes of increasing the public's acceptance for the new coin, as well as improving its overall appearance and durability.

Interest in the prospects of issuing a smaller one cent piece began to gain legislative support in the early 1850s, but it wasn't until 1856 that Congress finally got around to approving the new coins. Formal authorization for the circulation of the Flying Eagle cent came on Feb. 21, 1857. The design for the small cent was prepared by James B. Longacre. Actually, the eagle motif used by Longacre was taken from a rejected silver dollar pattern, executed 20 years earlier by Christen Gobrect.

As many as 1,400 patterns, proofs, and restrikes of the Flying Eagle cents, dated 1856, may have been struck. The bulk of these were apparently distributed to influential members of Congress before the congressional act took effect, and many found their way into circulation. The 1979 edition of the Blue Book lists a price of $1,000 for specimens in extremely fine condition.

Production of the Flying Eagle cents was carried out in unprecedented quantities at the Philadelphia Mint.The largest minting of this short-lived cent type occurred in 1858, with 24,600,0000 struck. Blue Book value for extremely fine specimens of the 1858 coin is $42. Mintage figures for the 1857 date total 17,450,000 and coins struck that year carry a Blue Book value of $40 in extremely fine condition.

Switzerland has announced a five-franc commemorative coin to mark the centennial of the birth of Albert Einstein. Oct. 8, 1979 has been set for the actual date of issuance.Ordering details will be available from the Swiss Numismatic Service, Bern, Switzerland.

The Republic National Bank of New York purchased 532,400 troy ounces of Treasury Department gold, offered in December by the General Services Administration, paying between $211.50 to $217.50 per ounce.

Foreign banks and investment firms purchased 784,400 troy ounces of the 1.5 million ounces offered.