Once you've narrowed it down to low-mid carbon low alloy steel, it's going to be really hard to speciate. The main thing you get with 8620 is a little added chromium. You're certainly not looking at manganese, tungsten, or silver steels, where the differences are obvious. X-ray spec or spark emission spectroscopy are next on the list. Of course, comparing the sparks of both sticks for similarity would be helpful.