T Man was a CBS summer replacement radio program that ran for nine episodes in 1950 featuring Dennis O'Keefe as a Treasury Agent Steve Larsen. Three years earlier O'Keefe had starred in the film T Men (that time O'Keefe's character was named Dan O'Brien), which made him a natural for this series. Over the summer, the show had appearances by William Conrad, Paul Frees, Virginia Gregg, and others. Despite being a serious crime show, T Man had a light touch that was popular with audiences.
An unrelated 1956 Australian* syndicated series, T Men, featured Gordon Glenwright as agent Jack Ketch.** According to that show, "This is a great country, it takes a lot of money to run and keep it running. That's why we have taxes. Taxes are scaled so everyone pays a fair share of the costs according to his or her true income or profit. Let one citizen evade his lawful tax, and you, the honest taxpayer, get slugged a little more next year to make up for Mr. Smartypants."***
* So it's an Australian show about the American treasury Department. You have a problem with that?
** Great name, huh? The original Jack Ketch was an infamous English executioner in the 1680's, whose name had been conflated over the years to refer to Satan.
*** Take that, Tea Party!