CHICAGO (Reuters) - Silver SpongeBob SquarePants coins minted by a private company in New Zealand were among the assets seized by FBI agents from Peregrine Financial Group after its chief confessed to nearly 20 years of fraud last week.

Ira Bodenstein, the trustee in Peregrine's bankruptcy case in Chicago, said the coins were in a vault at the firm's Cedar Falls, Iowa, headquarters. The value of the takings was not immediately clear.

The coin disclosure adds a new twist to the case of Peregrine Finiancial Group CEO Russell Wasendorf Sr., who was arrested last Friday after he confessed to doctoring bank statements to make regulators think his futures brokerage had nearly twice the assets it did, leaving customers with an estimated shortfall of over $200 million.

Peregrine, which operated as PFGBest, filed for bankruptcy protection last week.

The brokerage has $24 million in liquid assets in its general operating accounts, not in customer accounts, leaving little to repay customers, according to a filing from Bodenstein late on Thursday.

The filing does not say how much is in the customer accounts.

Peregrine ran a unit called PFG Precious Metals Inc, which offers investors "whole sale prices, fast & fully insured shipping" for gold, silver and platinum coins, as well as novelty items created through a partnership with the Auckland-based minting firm.

Customers from as far away as Bulgaria bought coins through the program, using Paypal accounts or credit cards to fund the purchases, said James Koutoulas, CEO at Typhon Capital Management. The coins were stored in a vault in Iowa.

A four-coin set of SpongeBob Squarepants, housed in a "distinctive" treasure chest, went for $259, according to a website that displays both the PFGBest logo and that of the New Zealand Mint.

Each coin in the set shows a character from the Nickelodeon animated series and bears the inscription "IN SPONGEBOB WE TRUST."

The mint told local reporters last week it was paid in full by PFG for the coins.