Double Portrait Ancient. Too Worn To ID?

I know that I have been asking a lot of "identification" questions lately. I appreciate you patience with me.

I picked this up figuring it would be a rather easy id for me, but it is turning out to be anything but that. I never realized just how many different double portrait ancient coins are out there. Add the condition of this coin and being a novice, I am not doing too well.

I don't have a scale accurate enough to weigh it. It measures almost 17.5mm on the longest side.

In my research I have found some that have similar head shapes in the portraits, but none exact. The three closest matches that I could come up with are (in no order):

1. Julius Caesar and Augustus
2. Gaius and Lucius
3. Senate and Roma

Any help is appreciated.

Doug