Professor Hynek's contact gave him a five-digit street number for a meeting. Presumably that is a Washington, DC address since no city was named. Street numbers in Washington, DC only go up to four digits.
In the epilogue describing the actual events depicted in this episode, the graphic which says "When Air Defense Command sent up two F-94 interceptors to investigate ...", it shows F-86 Sabre jets instead of F-94 Starfire aircraft.
The General says that Truman will be gone in six months. He must be prescient, because elections are held in November and the President is sworn in January of the following year approximately two months later.