how to check version of AdvFS

This is a 5.1A server that was upgraded from 4.0F, but I don't think AdvFS got upgraded.  I thnk it's still in like that compatability mode thing, and still back at v3 instead of v4, but can't find any way to tell.  I am building a 5.1B server from scratch, so it will be AdvFS v 4, and then I will be doing a vdump | vrestore from the 5.1A filesystems to the 5.1B filesystems, but am concerned about compatability issues with those uitilites.

Thanks for the help.