NEWOBJ class argument isn't a type object

1

I am trying to help someone to restore some data.
I have the var folder, but I am not sure which Plone version they used. Is it possible that this error can come from 'wrong versions'. I tried with 5.1.6 and it give me this:

/buildout-cache/eggs/ZODB-5.3.0-py2.7.egg/ZODB/serialize.py", line 615, in getState
return unpickler.load()
_pickle.UnpicklingError: NEWOBJ class argument isn't a type object

PS: Content types are Archetype, I think

2

The logs does not contain the Zope version? With the Zope version it is easier to find the Plone version.

3

Unfortunately, I have only (been given) the Data.fs and a buildout from 'when they tried to upgrade it' (from 3 years ago), the rest was lost (not backup-ed)
.