I have been looking at older Red Sox jerseys (1940s) including one that I own (a Bobby Doerr). The description of these jerseys usually says that the numbre and/or the team name has been restored. Sometimes it mentions that the jersey was sent down to the minors or came from the minors.

Can someone explain to me the reasons why numbers/team names were restored? Is this because jerseys were recycled for multiple years? Were jerseys sent between the minors and majors? How does one get a relative level of comfort that these old jerseys were in fact worn by the player in question (determined usually solely by the number)?

Thanks in advance for any help.