Vintage 76’ers team slides

Hello friends. Trying this post again. I collected sports cards and memorabilia from 1981-1994. My dad and I found these team slides in an antique shop many years ago. I started going through my collection recently. I'm looking for information. My guess is that they're from 1973-1977 based on Gene Shue as coach. I'd like to know if anyone has come across something like this before. Are they rare? Any information would be appreciated. Thanks in advance.