[Ensemble Production Interface] Can anyone tell me what this means?

AFAIK, this is an 'old' feature in Ensemble to allow you to have two different sets of config for a component so that you can quickly switch between them.  For example, you could use it for switching between different environments for testing interfaces. You would have a different class, but the same 'Name' in the production.  I suspect you've got this duplication inadvertently.

But, my recollection on this is hazy, so perhaps someone else can add a better explanation.

As Liz says this feature has been in Ensemble for about ten years. One very obvious use case in development is to have a file based BO as a duplicate of a TCP BO so you can cut out all the complexity of testing with a real target system.

To add a duplicate you just add another config item to your production with the same name.

Whichever one is selected from the pull down will start up with the production.

To remove a duplicate you select the one you want to delete from the pull down and delete the config item from the production. The other one will be left behind. Or you could edit the XML to remove it.