"Five Minute Mysteries" was a wonderful little show syndicated by NBC in the 1940s, used by stations as "filler" after sports broadcasts or to fill a short slot on their schedule. There are several episodes of the program floating around but I'm not sure the entire series has been found.
Program 25 is titled "Signal Block" and was transferred from original RCA Syndicated Program vinyl transcription, matrix number ND5-MM-3229-8B. The disc is dated December 22, 1947 in the matrix.
I'll drop in more of these in the coming months on the blog - I have two discs from the series.