FreeBSD deleted some compat code in the kernel some time ago, and it turns
out that restore used that to read old dump tapes, so we broke old dump tapes.
So you can't use FreeBSD's unmodified.
So 60011 is OFS_MAGIC and 60012 is NFS_MAGIC. Both of these are variants
on UFS, but really old. And given they are at different offsets, you'll likely need
to reverse engineer the offsets used for the platform's dinode.
dump from 4.4BSD had 'natural' types (so long was used which would affect the
offsets). It seems to be able to read both NFS_MAGIC and OFS_MAGIC tapes,
but you'll likely have to hack together u_spcl that's specific to the platform which
may take a little trial and error if you don't know what the typedefs for daddr_t
etc are. There's also a 4.1 dump/restore you might need (available in the 4.4BSD
Alpha archive and likely all earlier versions in TUHS).
Without more specific data it's hard to know if there's an extant binary that
can be run in emulation to read these tapes.
Warner