Does Colt mark anywhere on there guns when they do a factory reblue?

I heard they make a mark somewhere on the gun when the factory does a reblue job.. Is that correct?
And where would they mark them.. (maybe under the grip?)
I am mainly talking about on a Python, but could apply to any guns they do restoration work on.
thanks

Well since no one knows the answer to that question i decided to call Colt and ask them..
Answer:
No, Colt does not mark the firearm anywhere when it is sent back for re-blue or re-nickel work.
They say if you want a record of it to keep your receipt.