A glass mag float would definitely get it off. It's such a rough scraper.
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4083
If your nails can do it, a mag float can do it better.
http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=4083
If your nails can do it, a mag float can do it better.