Still got them in stock at work, they were commonplace in old TV sets.What? A dual capacitor? Sounds useless/pointless. My guess is that it would be a feedthrough capacitor. Check the resistance between the outer two legs; they should be connected together internally.
Hmm... Looking at the datasheet for the voltage regulator, it appears that the middle leg of C2 goes to pin1 of the regulator which is the + input:On the board C1 & C2 are clearly labeled and each "capacitor" had three legs with the ground in the middle.