Black triangle with central orange light moving slowly across sky.

Observers were up to five children ranging from 8 to 13 years old  I was ten and a half.  
We were in a clearing behind camps on the eastern shore of Webber pond in Vassalboro or East Vassalboro, Maine chasing fireflies.  
I distinctly remember looking up and seeing this black triangle with a peculiar orange light source in the center.  It was moving from East to West very slowly towards the pond.  There was still some dusk light coming through a solid overcast layer of thick Cirrostratus or altostratus cloud.  I distinctly remember several of us saying at once, "What is that"?  
It was moving very slowly and made no sound.  An airplane would have made sound.  We watched it pass directly over head and watched it until it went out of sight behind some trees.  
Visually it was about the size of a triangular tortilla chip held up at arms length.  The light in the center was a distinct, but not bright orange in color.  It did not illuminate things below it.  It was like looking up into something strange.  
It passed directly overhead.    We weren't scared, just real curious.  
My Mother vaguely remembers us telling her about it, but none of the adults were interested.  At this point no one else seems to remember the incident, but it has haunted me all my life.  
Maybe someone else can make sense of this.  I have been an avid skywatcher ever since.
Date may be approximate, although the witness does not indicate that fact.  PD