This is the only 1975/76 Topps Hockey cack case I can recall ever seeing.
Mastro Auctions offered it in their April/May 2008 Sports & Americana Catalog. The case has three 24-count rack-pack boxes, each holding 42 cards.
BBCE Auctions sold this single 1975/76 Topps Hockey rack box for just under $15k in November 2023.