If 5D III has S/N looks like this (xxxxx3xxxxxx), there should be a "RED" tape inside the body that will match with your "L" lenses.
I'm curious why you think a 3 model might be different? I have a 1, and it works perfectly.
I think we are mixing different arguments here (and in many other threads on the same issue):
1. Do the "1" copies perform exactly
as the "3" copies? Well, maybe they don't (even though they cost exactly
the same) but the difference seems to be so sneaky that the answer could well be yes.
2. Is the resale value if the "1" copies exactly the same, for any and all potential buyer that will consider an used 5D3 down the road? I would say no, unfortunately.
3. Are Adorama (which certainly knows about the issue) selling "1" copies hoping that their customers aren't aware of/ don't care about the issue or are they selling "1" copies already "repaired" (read: taped) by Canon? In the latter case I think they should better inform the customers, particularly after Canon issued their statement mentioning serial numbers.
4. How you price the lower reselling price, the burden of dealing with ultra-picky buyers, the uncomfortable feeling to be deceived by Adorama versus the additional delay in shooting with the much awaited new camera? It really depends on everybody's needs, but in any case everybody must be free to make her choice: waiting a couple of months or switching to a more customer friendly dealer are both legitimate decision in my book.
So in my opinion whether the light leak issue is a real issue and how to deal with it now that it has been so heavily exposed are two different discussion and answering in the negative to the first question (as I would tend to do) does not conceal the need to deal with the second. Ironically, all these big stores that greatly profited from the expansion of internet over the brick and mortar stores need also to deal with other aspect of the internet expansion, such as the over-exposure of a not so important issue.
p.s.: Sorry for any typo/ misspelling I may have made, hope you won't weight my arguments based on my English