This BETA mount was designed to modify and adapt a nFD or FDn 28mm f/2.8 lens to use it with EF DSLR Cameras, along with these part:
https://shpws.me/Sa3T aperture arm for nFD 20mm f/2.8
For more aperture arms please visit the store main page:
https://www.shapeways.com/shops/lensmounts
Follow this link to see the tutorial:
https://youtu.be/Jiv1HAlwF68