Question: I'd like to know if there is an easy way of deleting all faces which share ALL of their vertices with another face.

I imported a model from a .dae file and merged vertices by distance. This has created strange 'double' faces whose vertices are completely shared.

I can manually delete the duplicate faces one at a time, and a single face remains.

[![All the face's vertices are shared with the one beneath](https://i.stack.imgur.com/cnTyj.png)](https://i.stack.imgur.com/cnTyj.png)

[![I can select and delete one face](https://i.stack.imgur.com/X22nP.png)](https://i.stack.imgur.com/X22nP.png)

[![The other face remains](https://i.stack.imgur.com/17Xuj.png)](https://i.stack.imgur.com/17Xuj.png)

Answer: 
I don't know if you can call it from the UI, but the `validate` Python function will remove the extra face. Switch to Object mode, select the object you want to fix, and run this in the Python console

```
C.object.data.validate()

```
Merging points by distance should take the desired effect. In edit mode go to mesh - clean up - merge by distance, or select the geometry then M - by distance.