Topps released all sorts of button sets over the years, starting with 1956's Baseball Buttons. They then began issuing humorous pin sets, most of them metallic, on a semi-regular basis in 1960 with Funny Buttons although there were points they became sporadic. 1975 saw a test set called Big Bad Buttons and it's safe to say they are difficult to find today.
The year prior had seen a full retail release of Batty Buttons, which for my ten cents is the best of the non-sports bunch. So the fact the Big Bad Buttons test was a clear failure in '75 must have been a surprise to Topps. This is how they arrived at the test stores (thanks to Friend o'the Archive Rob Lifson for these two images):
Topps handily provided a checklist on the back of the test envelope:
Again, not at all that pithy of a comment. These really are hard to find and I had seen only a handful of images prior to my recent acquisition. Some Topps test issues are scarcer than others and the Seventies offer a good share of difficult ones.