Thanks to a recent post about Opening Night Playbills, I found out that 2 of my Playbills that I bought at the Flea Market were from their Opening Nights. Is there a certain way to know if a Playbill is from it's Closing Night?
Nope. No 'special' Playbill is issued for a show's Closing Night. They simply use the same one they've been using for that month.
Also, the Opening Night Playbills aren't just used for Opening Night. They continue using that day's Playbill for the rest of that month. I've obtained countless Opening Night Playbills of countless shows simply because I saw the show a few days or weeks after it opened and they still had the Opening Night Playbills in plentiful. I actually don't think they reprint more for that month -- they just fill the month's quota with those Opening Night Playbills.
Both Les Miserables in 2003 and Rent in 2008 have had specific covers/Playbills made for their closing night. As far as I know they are the only shows in the last 10 years to do so, if there have been any recently or previously I have no idea.
Besides that both Closing and Opening are whatever playbill that was used for the month. The one difference is that the Opening Nights may have a sticker to acknowledge the event.