sankaranarayanan parasura: where was SCM specified in the input? You need to be aware that SCM is an optional product not installed at all sites. My site, for example, does not use it and therefore your advice is totally inappropriate here.
I think I have answered for a twisty interview question. I understand what you have said is right.
Each installation will have its own standards to maintain different libraries to differentiate it.
My answer is for one such type of installation which has SCM for maintaining its elements.
If we should not read the source code and identify means it has some clue external to it.
Either it can reside in designated library or SCM defined and it is dependant on installation.