Howard Local Posthttp://zenius.kalnieciai.lt/america...usa/usa.html
The Howard Local Post was started in 1972 by Howard Du Bose of Durham, N.C. The Sherlock Holmes Old Radio issue was #42 in the series, issued on May 18, 1976, influenced by the Sherlock Holmes radio show (Mr. Du Bose was a professional radio engineer in the early '70s). There were 750 stamps printed, in 30 sheets of 25, and 150 First Day covers.
Howard says "I combined my interest in collecting stamps, reading mystery novels (I started in Viet Nam with Nero Wolfe), and working in radio. I did several radio stamps. I only did stamps about what I was interested in. I had a total of 55 issues, some of which are still for sale! "https://www.trussel.com/detfic/sholmes.htm#Howard
Note: 3 on eBay
, all postally used
Perhaps labels only used as cartoons.