50th Anniversary prototype logo?

So when looking at Astros hats, I occasionally see an "A" logo that is usually labelled as a 50th anniversary prototype logo. However, aside from these hats, I can't find any information about this! Does anyone have some backstory on this logo? Pic for reference.

https://preview.redd.it/hz5obtgi973b1.jpg?width=1079&format=pjpg&auto=webp&s=726e7adb2b5bfb58321ba1831f653efbb42a71ae