The Pathfinder-medal was a one-time medal earned by Agents who were at least Level 3 during Year Ten of Ingress.
Mechanics
This medal was awarded to all Agents who were Level 3 or above on 21. November 2022. Bronze was set at Level 3, Silver at Level 9, and so on. Onyx/Black was earned by all 
recursed Agents, no matter their level. The Agent also had to have earned some AP since the Pathfinder Medal was distributed.
Strategy
This medal is no longer earnable, since it has been discontinued.
Typically, there is a double AP event before these medals are released. Since this medal counts an Agent's Level, it is advised go for anything (legally and fairly!) that will make them level up quickly. Advanced fielding, destroying enemy Control Fields Δ, capturing Portals will do. A plan will make it infinitely better and more efficient. An Agent can also use Apexs to achieve double AP (or together with the usual double AP event prior to the release of the medal "quadruple" AP), making their trips much more effective. If an Agent is at least Level 8, an Agent can also aim for medals they are missing. By achieving higher-tier medals early, it removes the obstacle of needing to grind a specific medal. Otherwise, it can potentially put them a tier down on this medal.