I've come across another reference to Joseph Zeffertt of New York in 1894. This one shows he is the same as Jimmy the Swiper mentioned in The New York Times.
The World - New York
28 January 1894
"THREE BOLD YOUNG CRIMINALS
One A Highwayman at 12 - Two Others' Aged 12 and 13, Caught in the Act of Burglary.
Joseph Zeffertt wants to be a b-a-a-a-d boy, and he is travelling the high road towards success in that line. He is only 12 years old and lives with his parents at No. 227 east Seventy-fourth street. His first appearance in a police court was about two months ago, when he was taken before Justice Grady, at Yorkville, charged with holding up a blind man and robbing him of 54 cents. he was then allowed to go home on his promise to reform. He was fairly good until Friday afternoon.
At about 2 o'clock on that day he met Mambe McCarney, a twelve-year-old school girl, at sixty-seventh street and Third avenue. She held a pocketbook in her hand which contained a $5 bill that her teacher, Miss Foy, at the school, Sixty-eigth street and Madison avenue, had sent with Her to get changed. Joseph promptly seized the pocketbook, took out the $5 bill and threw the empty wallet in the child's face. He darted up the steps of the elevated railroad station, and, though Detective Weller, of the East Sixty-seventh street station, gave chase, he managed to get away. The lad was arrested in bed the following morning.
He was taken before Justice Koch, in Yorkville Court, yesterday, and was committed to the care of the Children's Society pending his trial."