The most common areas I see nickel fail are right on the side of the barrel at the muzzle end and under wood stocks. If the nickel gets worn enough that rust can form under it then it's going to flake off.

I would be trying my best to shove people out of the way to get a good priced nickel plated 13 in good condition. I can't even find a blued steel model 13 in my area. All I ever see are run hard and hung up wet 65's that are shot loose.