It is my belief the Cox and Brinkman yellows are all MB cards, but I do keep a pair of each with my MB and Topps 1968 sets because PSA and the old Catalogs included them as variations to the 68 Topps set.
Not sure if Carlton Miller still posts here but he has been my go to expert on the Topps MB set. Here is an article he did on it
https://r.search.yahoo.com/_ylt=AwrE...Fd3pYN71avF.4-