To be honest I didn't notice it? What it might be is a notation for the keyer switch under the cover. If you take the cover off there is a micro switch with a lever that you can use the tip of your finger instead of a key. I suppose in an emergency you could take the cover off and use it. I contemplated making a push button to operate it but didn't do it.
what mark is under the key? moon?
To be honest I didn't notice it? What it might be is a notation for the keyer switch under the cover. If you take the cover off there is a micro switch with a lever that you can use the tip of your finger instead of a key. I suppose in an emergency you could take the cover off and use it. I contemplated making a push button to operate it but didn't do it.