The Solution

We are at the end of our mystery - and here is the final solution.  Placing Block 1 and Block 2 alternately - set them as shown below.

 

This is the completed quilt - measuring 48 1/2" x 48 1/2", including seam allowance.   You may now add the borders

Note:  Twin measures: 60" x 84"
           Double measures:  72" x 84"