Lobster wrote:

Doors are very old (and do have this film reinforcement on the
back), so maybe predate some regulation or other?

Mine are about 15 years and I think were made (or at least re-badged) by
Stanley, they have a greenish colour backing film, and on closer
inspection a sticker that says "ACMETRACK please do not remove" is that
similar to yours?

Do report back on any successful (or failed) attempt at cutting them :-)