I thought Pearson and Wilson were manufacturers of Sixers pieces-
Did Sand Knit ever make the Sixers jerseys? It does have an exclusive tag.
The 76ers switched to Sand-Knit for the 1986-87 season - Erving's last. From 1976-77 thru 1985-86, Erving wore Wilson Sixers jerseys.

I'm guessing someone got their hands on a blank Sixers team jersey and customized it. The size is too big for an Erving gamer and they put the wrong style numbers on it

I posted it on another thread...that guy had a number of Sand-Knit hoops jerseys. Some looked to be team issued and some were the retail authentics.