Section 39: Article posted by mistake

When an article is delivered to the Postmaster-General and has thereby become liable to postage and the Postmaster-General is satisfied that the article has been delivered to him by mistake, he may cause the article to be opened in the presence of an officer of the Postal Service who may return the article without charge to the person interested, unless the article contains a letter or manuscript liable to postage, in which case, the Postmaster-General shall retain the article until the full rate of postage on the letter or manuscript has been paid thereon.