1968 Topps Yellow Letter Brinkman/Cox — Topps vs. Milton Bradley?

[raineybt]

Hey all —

I'm trying to pin down the true origin of the yellow letter variations for Ed Brinkman and Casey Cox from the 1968 Topps set. Specifically, I’m wondering if there are actually three versions of each card out there:

1968 Topps White Letter (standard Topps issue)

1968 Topps Yellow Letter (pack-pulled variation?)

1968 Topps Milton Bradley Yellow Letter (from the Win-a-Card game)

There’s some confusion out there because at least PSA has slabbed cards both as "1968 Topps / Yellow Letter" and "1968 Topps Milton Bradley / Yellow Letter." So the question is — were any yellow letter Brinkman or Cox cards actually pulled from Series 1 Topps packs in 1968, or are all of them Milton Bradley cards that have been misattributed over time?

For reference, here’s a solid article on the MB set:
A Tale of the Yellow Back: 1968 Milton Bradley Set – Sports Collectors Digest

I’d love to hear from anyone who has insight - as a Senators collector who's now focused almost exclusively on variants, I have to know whether this is a problem of broad lack of knowledge (including at PSA) or if these two cards are similar to the White Letter variants from 1969.