Did NASA receive a tax refund on a diamond window when it left the Earth aboard a space probe?

Question

According to Hughesscgheritage.com:

“Probe” is an export; diamond duty saved—Hughes News January 6, 1979

The cost of HAC’s highly successful Pioneer Venus mission was reduced by $12,474 because of an agreement established 10 years ago between the U. S. Customs Service and Space and Communications Group.

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Since the U. S. Customs Service considers the Pioneer Venus mission spacecraft to be exports, the $12,474 duty paid on a 13.5 carat diamond window manufactured by D. Drukker and Sons in Holland was refunded to Hughes, which then credited the amount to NASA’s Pioneer Venus account.

Is it true that NASA received such a tax refund?

Answer 1

Hughes Aircraft Company received the refund.

A first hand account is given by Bruce Leeds in his article What the Heck is Drawback and How Do I Use It?

Early in my career I took a position as Import Manager at Hughes Aircraft Company, an aerospace company in California. Hughes had imported a small natural diamond window (the size of a penny), from the Netherlands for use in a spacecraft. U.S. Customs classified it as an optical element because it was used to filter light, as well as rays, and Hughes therefore had to pay a considerable duty on it. The window was incorporated into the Pioneer spacecraft and launched from Florida to the planet Venus. Taking advantage of a ruling that said launching a spacecraft was considered an “export” for drawback purposes, we prepared a drawback entry, and received a refund of the duty paid...

So Hughes had to pay a duty when they imported the diamond, but they got a refund when they "exported" it.