# Forge Viewer shows different data from Model Derivative data on IFC file

This is a process that I’ve always used. First I call the bulk data from model derivative for further structuring. But this time the derivative data is confusing. Because when I use getProperties from viewer it shows external id with expected format(0/0/0/145/79) but when the same element is called from derivative api, on the field of external id, ifcGUID (11h5ts\$FhghhDGbOs) is written.

In short I can not get external id of element from derivative Api but it can be found from viewer.
What could cause to such confusion ?