What is that putty on windshield pinch weld

What is that putty that is used on the pinch weld window frame? Seems it smooths out the rough imperfections on the pinch weld. It's white, painted over and been there for 45 years. Replacing front and rear windshields. Do I need to replace this putty stuff when I install new gaskets?
If so, where can I buy it? Thanks.