Paramount started building tandems in 1969. Prior to this time, only special team tandems (like Olympic bikes) were made.
Serial Numbering: The first phase started in early 1969 and continued to the middle of 1970. It consisted of the following fields:
•Month Code: This one letter code corresponds to the month with A=January, B=Febuary and so on. Because I is not used, September=J and December=M.
•Year Code: This two digit code is the last two digits of the year - 69 is 1969.
•PT:This code indicated a Paramount Tandem.
•Sequence Number: This three digit number represents the nth frame and/or fork scheduled during the month.
For example E69PT109 was a Paramount Tandem built in May of '69. It was the 9th tandem of the year.
The second phase started in Mid-1970 when Schwinn started using the standard numbering system (and probably a common bottom bracket) with the company's mass production. For example, FF018524 was built in June of 1970, serial number 018524.
All Paramount tandem production had ceased by the end of 1979."