Should be I think -8 or somewhere close (not common), I use a -4 with dichroic coating as well as an additional layer of an active welding filter. Even a scratch can be problematic. I would never trust a 1/1000" plastic filter for anything not replaceable even though the active filter may only be 1/10^100th thick on either..
It's not like the government would ever make it illegal to own water, don't think about it too much. It already passed us, and soon we will be up to our necks in contamination. Dune, https://en.wikipedia.org/wiki/...