personally, if there is no way to tell what company made said components, like the previous owner had no receipt or couldnt remember what kind they were, then I would buy new shit. I only trust my own work unless backed by receipt/knowledge from the previous owner. I might just be paranoid, but I dont want to chance the whole build because of retainers/springs I am unsure of..........this is all based on IF they are aftermarket....but as KAI mentioned earlier the magnet test is a good start.