Officials at the National Postal Museum are hoping an auction of obsolete revenue stamps will deliver enough revenue to bring new exhibits to the museum.

Approximately 35,000 revenue stamps, which were placed on items to prove payment of taxes on them, will be auctioned Saturday in New York City. It could bring in an estimated $2 million to an acquisition fund for the museum, though the museum’s Registrar Ted Wilson stressed that’s just an estimate.

“It’s anybody’s guess,” Wilson said of the potential funds generated from the auction.

The Postal Museum plans to keep about 400,000 revenue stamps and donate some of those to various other museums and organizations.

The acquisition fund will enable the museum to purchase stamps to add to the National Philatelic Collection.

“It will benefit the visitors to the museum,” Wilson said. “People will be able to say that this is the best American collection they’ve seen.”

Wilson said the fund is necessary because the museum could no longer rely on donations alone to fill the collection.

“People have been incredibly giving over the years. We’re at the point where those gaps are difficult to fill in with donations alone,” he said.

Wilson Hulme, curator of philately for the museum, added that the museum is looking forward to improving the collection with new stamps.

“While the National Postal Museum has an extraordinary holding of philatelic materials, there are some gaps in the collection,” Hulme said. “For example, we are missing mint singles and examples on-cover of some early stamps issued by the United States and by the Confederate States of America. We plan to use the proceeds of the sale to help us obtain the needed items.”

The Internal Revenue Service transferred about 7.8 million duplicate revenue stamps to the Smithsonian from 1954 to 1977 with the understanding that they would benefit the national collection.

“We’re fulfilling the wishes of the donor,” Wilson said.

The transfers from the IRS stamp collection contain as many as 50,000 copies of 1,900 different types of stamps, and the museum faced a challenge of what to do with such an abundant collection.

“It would be like having 50,000 of the same model automobile at the History Museum,” Wilson said.

“As time went on, people realized it’s not that easy to get rid of 7.8 million stamps,” he said. “The revenue stamp market is small. In some cases, we have 50,000 copies of a stamp where there is only one known one in private hands.”

Wilson said the main challenge for the museum was making these stamps available to collectors without devaluing them.

“We said, ‘Let’s see if we can come up with a plan to get as many copies out to collectors without overwhelming the market,’” he said.

To prevent that, the museum is releasing the stamps over time. Highest value stamps will be auctioned first, followed by medium-valued stamps, and lower-valued stamps will be sold to individual stamp dealers.

The auction this weekend will include 135 of the most valuable varieties, including three copies of the rare 1 7/10 cent wine stamp. Only one recorded example of this stamp is currently in private hands.

The government began using revenue stamps during the Civil War on both proprietary goods and documentary transactions to prove that taxes had been paid on them.

In the 20th century, revenue stamps evolved into proof of payment for “sin taxes,” such as tobacco, playing cards, alcohol and even marijuana. The Marijuana Tax Act of 1937 mandated that any person who used, produced or prescribed marijuana must pay a tax on it. The previously unknown stamp used to comply with this law will be part of the auction.

The auction takes place Saturday at the Four Seasons Hotel in New York City. For more information, visit https://www.postalmuseum.si.edu/revenuestamps.