Nauticam Piano Button

Does anyone know how to remove the piano keys on a Nauticam housing? I need to replace the o-ring on the SET button shaft but I can not figure out how to remove the piano lever.

I have the NA-7D housing and I neglected to send it in for service this year. I have a couple of quick trips coming up so last night I inspected the housing and found the c-clips on the set button shaft were corroded. Apparently moisture is entering at this location. I can remove everything necessary to replace the 0-ring but I can not figure out how to move the piano key out of the way. I have another Nauticam housing that I can steal parts from until I get around to sending both housings to Reef Photo for servicing. I doubt that I have time to send the housing into Reef before my upcoming trips but I will call

Thanks,

TomC