Booker contacted his bank, Green said, and it sent him a copy of a deposit slip indicating that the $500 check, along with another for $10,000 from Market East Associates L.P., had been deposited in an account in the name of Next Generation CDC, a nonprofit headed by Mondesire.
If Booker "had not received the deposit slip, he would not have known about the $10,000 check," Green said.
Booker, along with fellow NAACP officers Donald "Ducky" Birts and the Rev. Elisha Morris, have been calling on Mondesire to answer questions about the checks and the organization's finances, but have not received a response.
Mondesire declined last week to comment on the matter, saying, "I have nothing to say. This is an internal matter of the NAACP."
Calls and an e-mail seeking comment from Mondesire on Monday were not answered.
Maureen Garrity, a spokeswoman for Market East Associates, an investor group seeking the city's second casino license, on Monday said the donation was meant for the NAACP's ACT-SO program, which encourages high academic achievement by African American youth.
The $10,000 check, a copy of which was acquired by The Inquirer, was dated Sept. 9, 2013. A copy of the Oct. 10 deposit slip showed the two checks were deposited into an account named for Next Generation CDC.
Garrity said Market East sent a letter to Mondesire on March 12 asking him to explain where the $10,000 had gone. She said he responded a few days later saying he would provide documentation of how the money was used.
"We expect to hear something from him soon," Garrity said last week.
Mondesire has endorsed the group's effort to build a casino at Eighth and Market Streets.
Booker, Birts, and Morris also questioned whether money from the national NAACP was being funneled through Mondesire's Next Generation CDC before going back to the NAACP. Records show the Next Generation CDC's tax-exempt status was revoked by the IRS in 2011.
The dispute between the officers and Mondesire came to light in January in an article by the website AxisPhilly.
In January, the three officers said they had asked the national NAACP to audit the local chapter and take control of its finances.
The officers said Mondesire had been handling the chapter's finances for more than a decade and that they had not questioned him about the group's money.
They said they raised concerns in November at the NAACP's headquarters when they realized there was no heat at the building on Cecil B. Moore Avenue near 16th Street.
Green and fellow lawyer Gerard Egan, who have been representing the three officers, have called on the state Attorney General's Office to investigate the chapter's finances.