Postal Savings Officials - Who Bought Them?

Regular postal customers bought postal savings stamps. Who bought the officials? And what was the point of the postal stationery postal savings officials (UO70-UO73)

"what was the point of the postal stationery postal savings officials (UO70-UO73)"

Mail originating within the U.S. Postal Savings System. Government-to-government mail. Government-to-user mail.

All of these officials allowed the USPOD to get paid for delivering other government departments' mail.

The prior post is correct that postal savings officials were used for postal savings business (headquarters to post offices, post office to post office, post office to headquarters, post office to customers, post office to bank). There is also a postal card, UZ1, which was used by post offices to report statistics back to headquarters.

As the Savings system was within the Post Office Department, it was more an accounting tool than anything else. The postal savings system was intended to pay for itself out of the 1/2 percent differential between the interest earned by the government on savings deposits (which were placed with national banks) and the interest paid out to customers.

Thanks!