Not Long Now,
You're testing my knowledge of the finer points of the SSE scheme. If no one filed a CA1261/4114 (because the controller concerned had confirmed that each aircraft was maintaining the correct level and was assured that there had been no loss of separation) then there would be no need for a SSE grade.
If the incident was filed as a loss of separation but the subsequent investigation revealed that the Mode C was at fault, albeit within tolerance, then I am guessing that it would probably be an SSE P (potential).