This is a Taito Egret 29 arcade button.

On the Egret 29 there are two cutouts for card readers but most are not populated with anything.

This print is to populate the smaller of the two cutouts with a button that you can rewire however you please. Personally I wired this to coin so I no longer have to use coins or open the coin door.

This is great is you have a MiSTercade as many cores use coin as the select button.

I used a Sanwa 24mm button switch as the internals.

Photos are from a test version and some small updates have been made.

This now includes a cover for the larger card reader opening.

Note: This does require trimming a small section from the bottom of the control panel so that it fits flush.