As of Python 3.7.0b2 _frozen_importlib_external.PathFinder exists twice on sys.meta_path, and it is the same object:
$ python -S
Python 3.7.0b2 (default, Mar 22 2018, 20:09:00)
[GCC 5.5.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> print(sys.meta_path)
[<class '_frozen_importlib.BuiltinImporter'>,
<class '_frozen_importlib.FrozenImporter'>,
<class '_frozen_importlib_external.PathFinder'>,
<class '_frozen_importlib_external.PathFinder'>]
>>> print([id(p) for p in sys.meta_path])
[24427944, 24430216, 24517416, 24517416]
>>> |