Looks like a std. HBG ( BG X GSF) to me. You did not say what type of lepomis (BG HBG GSF RES ) were stocked. It could easily be a HBG backcross with a BG and be 7-8 years old. HBG can reproduce but they are a high % male and in lower #s. A LMB crowded pond will have some large BG/HBG etc and very few small ones.

Based on its size ,shape and coloration I don't think it has drifted back toward its GSF relatives.