Protest against postal rates in the United States
A registered letter sent by airmail from The Hague to Batavia stood out because of an imprint of a hand with an outstretched finger, printed in red ink. Such a little hand looks typically American. But it was not that little hand and the beautiful postage that made the letter special.
On the back, a small stamp was pasted that caught attention. A protest stamp! What was going on here?
The small stamp indicated in a slogan that half of the postage paid by means of stamps was in fact tax! I found the explanation on the internet when I typed in the search term 'National One Cent Letter Postage Association'. The 'National One Cent Letter Postage Association' was an organization founded to denounce the reduction of the first-class letter rate in the US from 2¢ to 1¢. The Association was founded in 1912 by Charles W. Burrows, who, after his retirement, had withdrawn from the book trade to dedicate his time to the campaign. Burrows believed that the 2¢ letter rate was unfair and that first-class users of the second-class rate were being subsidized by this measure. The first-class letter rate was 2¢ from 1885, and the second-class rate was 1¢ per pound. Large publishers of periodicals and the like benefited from the reduction, but small businesses such as bookstores had to pay the full rate. The organization had an office in Cleveland, Ohio. Leaflets and pamphlets were distributed there calling for support for Burrows' cause. In addition to the leaflets and a special stamp, Burrows had labels made in the size of a postage stamp and, just like a postage stamp, had them gummed and perforated. They were sheets of 5 by 10 stamps. The text on these labels was (loosely translated): ONE CENT / LETTER / POSTAGE in the middle, with at the top the HALF OF YOUR POSTAGE IS A TAX. On the bottom half of the label: ADDRESS NATIONAL ONE / CENT POSTAGE / ASSOCIATION / CLEVELAND, O. The labels were printed in red on white paper and were given away for free for use by owners of bookstores and stationery shops. However, one had to be a member of the association for 10 dollars per year. Although the labels resembled postage stamps, they were not intended to be used for that purpose. Nevertheless, some members did so, and usually this went unnoticed by the postal workers. There are three types of these labels:
Type 2 has a white top and bottom with red letters. This type is also printed in sheets of 50.
Burrows also had an imprint of the label applied to the back of his envelopes, accompanied by an explanatory text. Burrows continued his struggle until 1925, when he gave up unsuccessfully and dissolved the association. He died seven years later, on April 1, 1932, at nearly 82 years of age. He was buried at Lake View Cemetery in Cleveland, Ohio. But why such a label was affixed to the back of the Dutch envelope from 1931 is a mystery to me. Have you ever seen such labels on postal items? 
Mr. (or Mrs.) Vanger was clearly a philatelist who put together interesting postal items. Airmail and Registered Mail labels, various stamps, and probably a homemade hand. And finally, sticking a sealing stamp (that happened to be on hand) on the back.
It would not surprise me if there are more pieces of mail from this gentleman (or lady) in circulation.
Burrows continued his struggle until 1925, when he gave up without success and dissolved the association. He died seven years later, on April 1, 1932, at nearly 82 years of age. He was buried at Lake View Cemetery in Cleveland, Ohio. But why such a label was affixed to the back of the Dutch envelope from 1931 is a mystery to me. Have you ever seen such labels on postal items?