Montgomery County Police stated in 1987 that they believed Fred Howard Coffey, Jr. to be the strongest Person of Interest ever considered as a possible suspect in the Lyon Sisters' case.
It should be noted that his resemblence to the Tape Recorder Man Sketch, however strong, was not considered compelling enough evidence on its own to charge him. At the time, he was being tried in North Carolina for the murder of 10 year-old Amanda Ray, and North Carolina authorities - and Coffey's lawyers objected to MCP even questioning him.
There are discrepancies in the initial description of Tape Recorder Man and Coffey's description. Besides the age (50 vs 30), the height was given as "about 6 feet tall", whereas Coffey stands only 5 feet, 8 or 9 inches tall. It is not known if Coffey's photo - or any other photos - were shown to the witnesses who claimed to have seen Tape Recorder Man.
It should be pointed out that a "side by side" comparison of the Sketch and a photo of Coffey (or any other potential suspect) on the internet could be considered legal grounds to disallow any future witness identification of the suspect in court.
MCP seems to have dropped their interest in Tape Recorder Man about a month into the investigation, making official press statements which indicated that the man "might have been there for legitimate purposes", or "might not have been connected with their disappearance", etc. They never released either sketch after April 1975.
Coffey has since gotten off Death Row following legal appeals by a lawyer who has made his living and reputation in Death Row case appeals. That lawyer (mentioned previously in this thread) would almost certainly object to MCP questioning Fred today - for more or less obvious reasons.
Mention of Coffey's birthday being close to the disappearance date has been noted. In fact, there are two other persons of interest whose 30th birthdays were within a few days of the girls' disappearance as well. It is perhaps nothing more than a coincidence, but a very interesting one all the same.
Coffey was, in 1975, in a major transition point in his life. He had been in the Navy since age 17 (1962). Although he had only gone to school through 8th grade, he had made a promising career in the Navy and had attained the rank of First Class Petty Officer (E-6). Suddenly in 1974, he gets out with an honorable discharge - about the same time that he is charged (and convicted) for the first time of child molestation in Virginia. Coffey came from the Norfolk, VA area to the Metropolitan Washington, DC area to seek work as a Department of Defense Contractor. He applied for a computer programmer position with Vitro Laboratories on 1 April 1975, and began work with them later that month. He resigned suddenly on 31 July 1975, telling his employer that his wife and daughter had been involved in a serious auto accident. He used the same excuse later when leaving another employer. Investigation proved that he had lied both times about the accident.
Back to the subject of "coincidences", April first was only a week after the Lyon Sisters disappeared, and July 31st was only a week after Kathy Beatty was abducted, raped, beatten, and left for dead in a ditch.