I was sorting my dups and noticed these differences. If you compare the space between the purple Harrah's and the green " casino " you will notice that the space is different for all three. I know that the green ink printing was probably a seprerate step in the process, but you would think they would have better registration.
I measured from the bottom of the "a" to the green line and got the following from left to right:
1.5mm, 2.5mm, 3.5mm.
I only have one of the first two, but 3-4 of the last one.