Zenith marketed an optional protective soft felt bag for their high end Royal 500’s. Without the bag, many scratches would develop from the repeated sliding in and out of the leather cases. So these bags did a nice job of keeping the radio surface scratch free and protecting them from sunlight and dust.
Zenith also issued a warning slip about the possible discoloration from storing radios in their leather carrying cases without the bag.
Perhaps that is why some of the white radios are now an ivory color? And there are also coral radios that appear to have received a “suntan” from the leather case as the tan is outlined by the shape of the flap of the case. Just to be safe, I protect all of my finest radios in felt bags when they are not on display.
Below are some of the different styles of felt bags that I have been able to find. The most common is the one below with silver stitching and cord drawstrings.
Below are a couple of early bags for the first hand wired 500s. Note the black stitching instead of silver, and the ribbon drawstring instead of cord.
A very rare larger felt bag was made for the Royal 800 portable. (I have only seen 3 of these).