Is this a original 1961 7up Sign? I ask because I know Stout sometimes will make a run of reproduction signs. How can I tell the difference?

It looks like 1961 to me. If it's not a repo.

How can I tell if a repro?

I am not skilled enough in that department. I just know how to read the date code at the bottom. Sadly some repos are being made with date markings=(

Looks good color right back is right.

Highly doubt it is a fake sign. Be too much work, stamping it with the undulating waves, and so on, be easier to make other signs that are more valuable. Looks identical to other signs that have sold as original too (worthpoint.com). Nothing about it seems alarming to me.