I either use the search function on T206Resource
http://t206resource.com/Checklist.html or I go to the PSA website's population report
http://www.psacard.com/Pop/T206 and there you can open up a drop down box under a player's name and see what backs there are. I'm sure that there are other options, and I'm not sure if these are 100% accurate or not, but these are pretty easy to navigate. My guess that it is the red background Cobb at 15? Which player are you attempting a back run on?
