You have to enter the metadevice # not a softpartition (as root)

sudo metarecover -v -n d208 -p
Verifying on-disk structures on d208.
found incorrect magic number 207d100, expected 20000127.
No extent headers found on d208.
d208: On-disk structures invalid or no soft partitions found.
metarecover: max: d0: bad magic number in extent header

[ss0747@xxx] ~/scripts$ sudo metarecover -v -n d200 -p
Verifying on-disk structures on d200.
The following extent headers were found on d200.
Name Seq# Type Offset Length
d201 0 ALLOC 0 4194305
d202 0 ALLOC 4194305 4194305
d203 0 ALLOC 8388610 7233537
d204 0 ALLOC 15622147 4194305
d205 0 ALLOC 19816452 4194305
d206 0 ALLOC 24010757 4194305
d208 0 ALLOC 32399367 18874369

NONE 0 END 98933151 1
NONE 0 FREE 95313934 3619217
Found 11 soft partition(s) on d200.
Checking sequence numbers.
d200: Validating soft partition metadb entries.