Trying to identify this type of insulation and maybe some alternatives I can use to replace it with. It looks like foam to me. House was built in 1950s or so:
It looks like blown in cellulose insulation.
it was probably done long after the home was built.
I want to say popular after the 70’s. You can put other types over or replace it with any kind of batts or chopped blow in.
Big Box stores still sell it (I just checked on line) so if you need to add it or a very similar product is available.