[RustyW]

I have some of those in my toolbox. I'm an autoglass installer and used those plastic razor blades to remove labels and excess sealant off 80's cadilacs with anti-laserative windshields. They had an additional plastic layer on the inside surface and would be destroyed by regular blades.
Rusty

 

[RustyW]

I could add a link but dont know how[better stick to woodworking rather than computers].
Rusty

 

[RustyW]

www.crlaurence.com/ProductPages/C/CRL3000_3293.html.?Origin=