[Ronnie73]

You could use a back multiplier scale to determine a ballpark price but the market continues to change and move upward. Plus you have some big collectors getting out of the T206 set while new ones are coming in. It's best to follow what each front/back combo is currently selling for that you are trying to value. Look at successful completed auctions and sales for prices. There's no true scale to value a card combo. If there was, certain less known rarities would no longer be a secret. Learning as much as you can about print groups and the groups within those groups can be very helpful. Even though the backs are the same, depending on what print group a card is part of, can put it in a different level of rarity. So, best thing is, first be sure they are real cards. No point in doing a bunch of research for something that's fake. Check recent sold prices in multiple places such as eBay, PSA, and HA. Look at population numbers. Now I know these numbers are a mess but they can still be helpful when comparing one combo to another if there are no recent sales of a certain card but it has similar pop numbers as another card that recently sold, you could get an idea on price. The last thing you could do is just ask. But be sure to do as much basic research on your own first.