==Keystone > Senior Executive Service==

What does the SES insignia symbolize?

The SES insignia or emblem represents a keystone – the center stone that holds all the stones of an arch in place.

This represents the critical role of the SES as a central coordinating point between Government's political leadership which sets the political agenda and the line workers who implement it.

Sauce

https://www.opm.gov/faqs/QA.aspx?fid=fcd37029-d607-4fec-a8d6-faecbdb08eef&pid=40caa6fb-5788-4da6-812e-aa0fe8937cd8