The original Northlight playbill does state on page 10 where the cast is listed: Kathleen: from Now to Then
Jamie: from Then to Now
I probably read it before the show started but (knowing nothing about the story) didn't really know what it meant.
If I'm not mistaken, I believe the ATC-er MikeR saw the show at the Minetta and posted around that time that there was a similar placard at that theater somewhere in its lobby. However, (based on what I was told by that lead performer) a lot of people either didn't see it or didn't bother to read it because audience members (especially older ladies at matinees) would shout remarks at Jamie and Cathy at times during the show.