Thanks to Larry Eskridge for explaining what Barrie Wilson is wearing on the inner sleeve of the Something Magic album (full picture here)
In the ever-present search for odd-yet-hip-looking garments which all rock musicians must make part of their lives, BJ had apparently gotten hold of an old 'varsity' / baseball-style warm-up jacket (perhaps while the boys were recording on this side of the Atlantic - in Florida for this album, I believe, right?) commonly worn by American high-school students from the 1940s through the 1970s and still worn today in various new versions.
Said jackets usually were in team colors of one's high school and often had the high school's name or team nickname ('Bulldogs', 'Pirates', whatever ...) on the back and often numerals indicating one's (expected!) year of graduation, or the student's name. These jackets also sometimes served as 'Letter' jackets which the student would adorn with various emblems earned in athletic endeavors (mostly) and sometimes other extracurricular activities (band, debate team, student gov't, etc. etc.)
That thing on BJ's jacket, emblazoned with '61-62' if you look closely, is a basketball emblem which shows that the former owner was either a member of his school's basketball team that season, or, that perhaps the team won the local conference championship or some such that year.
More about this than you could ever have wanted to know ... except that the image is © Jay Rosenblatt
See also explanation of Chris Copping's tee shirt