I think all the yellow Cox and Brinkman cards are MB cards and not variations to the 68 set. But I still keep a pair of the yellow Brinkman and Cox cards with both my MB and regular Topps set because the hobby still generally recognizes them as variations. We have a resident expert on the MB set, Carlton Miller
( goheels), but I have not seen him post in awhile
Here is an article he did on the MB set
https://r.search.yahoo.com/_ylt=A0ge...Ga05pmnKmMxf8-
The issue is discussed in this link too
https://r.search.yahoo.com/_ylt=A0ge...14CdFDuWEdQUo-