He served as chief numismatist (person responsible for selling government coins) at the World's Fairs in St. Louis (1904), Portland (1905),[a] and San Francisco (1915).

His tenure as president proved controversial, as he purchased the privately owned journal of the ANA, The Numismatist, from the heirs of its founder in 1908, a transaction that some believed should have been on behalf of the association.

[2] By many accounts, including as told by Zerbe in his later years, his interest in coins was awakened when as an 11-year-old, a customer paid him with a silver French 50-centime piece, and the bank refused to accept it.

[1] A prolific writer, Zerbe published his first article in the ANA's journal, The Numismatist, in 1902; titled "Slugs and Stellas", it discussed certain rare U.S. gold coins, and was the first of more than 100 pieces he would write for that publication between 1902 and 1945.

[2] Numismatic writer David T. Alexander described Zerbe as "an energetic, self-promoting figure whose overall demeanor suggested a carny grifter rather than a distinguished numismatist".

[2] In 1902, President Theodore Roosevelt had signed legislation authorizing 250,000 gold one-dollar pieces to be struck by the Bureau of the Mint and paid over to organizers of the 1904 Louisiana Purchase Exposition in St. Louis as part of the government subsidy for the fair.

[2] Nevertheless, at the recommendation of influential fellow coin-collecting enthusiasts, Zerbe secured the position of chief numismatist to the St. Louis fair,[3] responsible for selling the coins and medals put on sale by the U.S. government, including the two varieties of the Louisiana Purchase Exposition gold dollar.

Pricing them at $3 (equivalent to $102 in 2023), an amount he stated was justified because regular-issue gold dollars commanded a premium, he also sold them mounted in spoons, jewelry and other items.

[14] Armed with letters of recommendation from St. Louis fair officials, Zerbe next secured a position as chief numismatist to the 1905 Lewis and Clark Exposition in Portland, Oregon.

Before he departed for Los Angeles to conduct more research, Zerbe aided those affected by the earthquake,[18] and spent ten days gathering data and photographs for a contemplated (but never published) book on the event.

[18] In 1907, Zerbe mounted an exhibit at the Jamestown Exposition in Norfolk, Virginia, and unsuccessfully proposed a $2 silver coin to be issued for that fair.

[26] Zerbe by then had enemies in the numismatic world, led by Thomas L. Elder, a New York dealer who considered him a charlatan and issued satirical medals accusing him of profiteering off the Louisiana Purchase dollars.

[27] Zerbe weaponized The Numismatist for the election, refusing to allow Higgins or Elder to be mentioned favorably in its pages, and representing their positions in a negative fashion.

[2] According to Bowers, Although details are not clear, it seems evident that Zerbe caused the ANA membership rolls to be padded by adding new members, men not at all interested in coins, simply to gain their votes for Henderson in the 1909 election.

At the annual convention, held that year in Montreal, Zerbe had 400 proxies in hand for his pet candidate, Henderson, while Frank Higgins had just a few dozen.

[2] After leaving office at the end of 1909, Zerbe tired of publishing The Numismatist, which did not make much of a profit, and in 1911 sold it to Montreal collector William Walter Coulthard Wilson, who donated it to the ANA.

Zerbe apparently profited handsomely on the transaction, receiving what ANA archival papers described as a "long price" for the periodical.

[28] Zerbe was appointed head of the fair's numismatic department, overseeing the sale of the coins and medals the U.S. Mint issued to commemorate the exposition.

Treasury officials agreed to allow him space for a salesperson at the Mint's exhibit, and the lower-denominations coins were sold there, with orders taken for the $50 pieces.

The full legal allocation for each denomination had been struck, but though Zerbe continued selling coins by mail after the fair closed on December 4, sales dropped through 1916.

It is the oldest numismatic organization in the Western United States, and describes itself as fostering a strong tradition of research and literary publication.

[2] On August 25, 1920, at the ANA convention in Chicago, President Waldo C. Moore called on Moritz Wormser, Chairman of the Board, to read a paper from Zerbe.

In his paper, Zerbe asked for a general circulation commemorative silver dollar, with the object of the coin to display America's desire for peace.

Zerbe's writing stated: "Our example as a democracy ... was a mighty moral force that won battles without number in the hearts and in the minds of those who ultimately proved that they had the power to topple thrones".

[33] The Chase Manhattan Bank Money Museum remained open until 1977, after which many of the pieces were donated to the National Numismatic Collection at the Smithsonian Institution.

In 1944, he was named an Honorary Life Member of the ANA,[22] and the following year was made historian of the organization, a post in which he served until his death.

"[27] Dodson wrote that Zerbe, despite his limited education, "accomplished more than the combined efforts of a host of learned scholars in publicizing numismatics at the grass roots level".