Acoustic Guitar Construction

What is the best way to approach a guitar repair when there is no label telling you what glue was used originally or since it was first made ? I saw some guitars for repair on e bay and that is the first question I asked myself. Is there a forensic system with maybe a microscope that works best ?

With the exception of Asian mystery advesives --- glues including hide, pva, ca and epoxy will breakdown with appled heat. As for the Asian junk I stopped working on those years ago.

Also, with the excetion of hhg all the residue must be removed prior to regluing.