What is a GREY ace?

Excuse me, could you please clarify what exactly is meant by the term "GREY ace"? Is it a specific term within the cryptocurrency or finance industry that I'm not familiar with? Or perhaps it's a reference to a particular type of investment strategy or asset class? I'm curious to understand the context and significance of this term, as it's not immediately apparent to me. Could you provide some additional information or context to help me better grasp the concept?