Leon, thanks for bringing this back to the top, as I was not reading the board in 2011. Those are some priceless hobby archives you have there.
T213-1 Coupon cards are on very heavy paper. The paper stock is thin compared to other cardboard series, but it is "Heavy" or dense in that the colors on the front do not show through to the back. Light paper, like typing or notebook paper, is not sturdy enough for colors not to be seen from the other side of the paper.
And, I agree with Jim that T216 Virginia Extra are much more difficult to find than a Coupon card. The T216 are another interesting series, in that it seems that if grouped by the front of the card, then they should be classified with the matching candy or E cards.