Angel Fish - ill or injury?

My sister has a lovely black angel fish and wishes to give it to me as her tank is too small; however on one side it looks like a patch of scales is missing. It looks shiny silver instead of the deep black; not fuzziness or Ich looking - just missing scales?)
There are no fish in her tank that would fight with it and cause damage; only other inhabitants are 1 platy, 2 neons and 3 "fruit" tetras.
Is there a disease that would cause scale loss? He eats well and appears healthy except for this patch. Her params are all normal (0/0/18). I am nervous about taking this fish without knowing for sure if it sick or just injured from being in such a small tank. She has a couple plastic plants and a tetra whisper filter...in a 10 gallon! :wall: she would not listen to me at all when she got it several months ago but now she is starting to feel guilty

the pics are really bad but I will post them anyway. she noticed the "patch" 2 days ago.....

I told her to do a water change and let me know how it looks by today. Hopefully she followed my advice.

I may just wind up taking it this weekend just to get it out of that 10G. It is truly a lovely fish and I hate to see it suffer......

Gah!!! I just called her and she has not done a water change yet......she (her hubby) has very old school ideas on fish keeping and tank maintenance! Drives me nuts!!! ("the fish will only grow to the size of the tank"....."I never used to do water changes, only once every year or two to clean the tank really good") :thud:
I will be taking the Angel tomorrow and it will live in my 29 gallon with nice perfectly clean water that gets changed (40-45%) every week! Poor baby......Now to catch the Otos that are in that tank so the Angel does not try to eat them! :nilly:

Got the angel today and she is fine...it is definitely a scrape. She is happily exploring my 29 gallon tank.