This set is the new DSS profile from Signature Plastics, and is designed by Cassidy Williams!
This is an add-on kit that contains 12 additional keys. Add it to the DSS Tecla Keycaps - Base Kit and you'll have everything you need to for a Preonic board (and then some!). The keys included are: grave/tilde (red), number row (1 through 0 in white) and backspace (red).
Photos show a Planck build, we're in the process of taking gorgeous photos of the Preonic add-on ;)
Other colors and combinations are available on Pimp My Keyboard.