While searching for various accessories to go with my Revox A77 MKIV, such as dust covers that accommodate leaving the reels mounted, and original remote control units, I discovered that there is next to no documentation online about the little port caps that came with my machine. One inmate mentioned them on here years ago but that thread was archived so I thought I'd start a new one focusing on the different types of accessories for the A77. These little plastic port caps say "Reserved for Beyerdynamic Microphone." Here's a pic of one below. They are completely unnecessary but still cool bits of ephemera...
