Hi,
The anonymous blocks Will Watch noticed came from custom objects created by AutoCAD Architecture (AEC objects) and the line types which are referenced by these blocks too.
If you open this drawing in an AutoCAD (vanilla) version which does not have the Achitecture Object Enabler installed, all these custom objects are converted into proxy objects (zombie objects).
Doing so, you can erase these proxy objects using the ZombieKiller app (on
Exchange Apps) and deeply purge the drawing with RadicaPurge (on
Exchange Apps too).
Attached the drawing after this cleanup (2081 proxy objects erased, 919 objects purged).