Mutilated Postal Stationery

What in heavens, is an Australian "N.S.W" postmark, doing, on a 2c US Postage?

Aerogram - a sheet of paper with a strategically placed stamp-like indicium that prepays air mail postage. After the message and the name and address of the recipient are written, the sheet is folded, sealed and mailed. No enclosures are permitted.

Cut Square - a section of postal stationery, cut from the entire, which contains the stamp-like indicium. Cut squares are considered less desirable than entires. While cut squares from stamped envelopes are considered collectible, cut squares from postal cards are not.

Cut-to-shape - the stamp-like indicium from a stamped envelope that has been cut from the entire and trimmed to the size of the indicium. A cut-to-shape piece is generally less desirable than a cut square.
 
Entire - 1.) an intact piece of postal stationery, that is, a piece of postal stationery that has not been reduced in size. Not a cut square. 2.) any intact cover.

Indicia - plural of indicium.

Indicium - 1) the stamp-like impression on postal stationery, 2) the imprint of postage made by a postage meter.

International Reply Coupon - a coupon sold by the post office that is redeemable by its recipient in a foreign country for return postage.

Postal Card - a mailing card produced by the post office, as opposed to a privately produced post card. A postal card has a stamp-like indicium. Postal Cards were first issued in 1873 [in the U.S.].

Postal Envelope - see Stamped Envelope.

Postal Stationery - a category of products which includes Postal Envelopes, Postal Cards, aerograms, wrappers, and international reply coupons.

Stamped Envelope - an envelope with a stamp-like indicium documenting payment of postage. Stamped envelopes were introduced [in the U.S.] in 1853.

Wrapper - a sheet of paper imprinted with a stamp-like indicium that can be folded and sealed around a newspaper or periodical for mailing. A wrapper is an item of postal stationery.