Building on the success of the collaboration between PTB, NPL & IMGC in constructing the combined optical and x-ray interferometer facility (COXI) for calibrating displacement transducers, PTB and NPL are collaborating by combining x-ray interferometry with scanning probe microscopy. This work is proving to be very successful and led to an Institute of Physics Select publication. PTB and NPL have decided to formalize the collaboration and are considering the possibilities for combining optical and x-ray interferometry with scanning probe microscopy. The principal application for the combination of these techniques will be the investigation of long range variations in the periodic structure of artifacts used for the calibration of scanning probe microscopes. Additionally, the collaborators will attempt to seek industrial interest for the development of the combination of these techniques.