What is this "transparency" and what is it made of?

At 22:51 18 September 2009, Brad wrote:
I am trying to remove the spray coating that was sprayed on my
transparency for shipping. Stuff has been on there for over 3 or more
years now and it might take me that long just trying to remove the
damn stuff.

Any advice from those who might have some experience with this
tenacious film?

Thanks,
Brad