Level 50 Cogs
Level 50 Cogs are presumably the highest possible level of Cogs. According to the Cog health formula for level 12+ Cogs, they would hypothetically have 2,666 health. The only known level 50 Cog was the Director of Ambush Marketing who made an appearance during Doomsday.
The only other instance of level 50 Cogs is the maximum level of Cog Disguises. Toons advance past level 12 when reaching the eighth tier Cog version of a Cog Disguise.