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.
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?