I took all four wheels off to ceramic coat them inside and out. I only looked at the tire size and didn't realize the front and rears have different offset, so there is a possibility I might be driving with the wrong wheel setup. Is there a way to tell without having to take the wheels off and maybe I got lucky putting them back on?

 

Inside the rim has the offset numbers printed. It'll say ET##. For example scroll down and you'll see an ET figure circled in yellow.

Go here to confirm the ET (offset figures) for front vs back:
https://www.wheel-size.com/size/mercedes/gle-class/

 

I get that. I was hoping there was a way to identify externally so I know if I got it right without having to take the wheels off again, or if I just need to swap one side.

 

Gotcha. Perhaps a mirror to see the interior offset stamps or maybe visually if something looks off based on the wheel arches and whether or not the wheels look more inset than you would suspect. You must have 20" wheels?

 

Cheers for the mirror tip! I was a bit skeptical at first, but the spokes are far enough apart to get a mirror inside. Only had to swap one side.

 

Nice! Glad you figured it out.

 

That's neat trick but if OP posted pictures of the design of the wheels we can run the wheels design through MBEPC and get the offset needed, looks like that is no longer needed though as OP seems to have it figured out now.