Post a picture of it and we can identify it. If it's from a 1st gen or '70 Camaro then it's the 8.2 10 bolt. If it's froma '71 to '81 Camaro then it's the 8.5 10 bolt. If it's from a 3rd or 4th gen Camaro then it's the 7.5 10 bolt. All 8.2 and 8.5 Camaro rear ends had 28 spline axles. The 7.5 had 26 spline axles up to '90 when it was upgraded to 28 spline axles.
What are you going to do with it?