Mount NV+ LVM1 X-Raid set on Linux.

I have a customer with an old ReadyNas NV+ which, after many years faithful service has finally died. It appears to have blown it's PSU (Swollen & Leaking caps, charred coils etc).

Searching the forums there are many references to mounting ReadyNas disksets & volumes on linux to recover the data.
As a user of Linux Mint17 (64) (a variant of Ubuntu 14.04) this seemed like the quickest route.

Since the NV+ is dead I don't have a record of the exact version it was running.
I did record the the 4 x 500G disks were in an X_Raid Configuration with ~1.3TB available.

I am nearly there.
We had 4 x 500G drives in the NV+ now they are connected, to a machine, running a "Live" Linux Mint 17(64) (Ubuntu 14.04) from a flash drive.
Drives are seen by the Bios
LVM2 is included by default in Mint17

From my records these were configured with X-Raid giving ~1.3 TB usable space which seemed reasonable.
I assumed that X-Raid is a variant of Raid 5, but when I inspect the drives with PVScan and the GUI, it shows only 3 drives as participating in the LV, the fourth appears to be blank, having no recognisable partitions.
Is X-raid in fact a variant of Raid4 with a dedicated Parity Drive?
What part is the fourth drive playing in the raid set?

I added System-Configuration-LVM, the GUI interface to LVM to the Live Mint.
LVM Sees the Drives, PVs VGs LVs, and even a Snapshot. Note these are LVM1 Entities

See image here
https://app.box.com/s/9rysct7ucqakxoffjvvndr7w479di724

And Running PVScan, PVDisplay, VGScan, VGDisplay, LVScan, LVDisplay confirm this

Note that sdac is not shown as a member

However when I try to activate the VG
vgchange - ay c
I get

device-mapper: reload ioctl on failed: No such device or address

If I browse /dev I do not see /dev/c/c , but I can see /dev/mapper/c-c
I have run vgmknodes, which fixed that populating the the /dev/c/c folder

Mount also fails

mint mint # sudo mount /dev/c/c /mnt -vvvv mount: fstab path: "/etc/fstab" mount: mtab path: "/etc/mtab" mount: lock path: "/etc/mtab~" mount: temp path: "/etc/mtab.tmp" mount: UID: 0 mount: eUID: 0 mount: spec: "/dev/mapper/c-c" mount: node: "/mnt" mount: types: "(null)" mount: opts: "(null)" mount: you didn't specify a filesystem type for /dev/mapper/c-c I will try all types mentioned in /etc/filesystems or /proc/filesystems Trying ext3 mount: mount(2) syscall: source: "/dev/mapper/c-c", target: "/mnt", filesystemtype: "ext3", mountflags: -1058209792, data: (null) Trying ext2 mount: mount(2) syscall: source: "/dev/mapper/c-c", target: "/mnt", filesystemtype: "ext2", mountflags: -1058209792, data: (null) Trying ext4 mount: mount(2) syscall: source: "/dev/mapper/c-c", target: "/mnt", filesystemtype: "ext4", mountflags: -1058209792, data: (null) Trying vfat mount: mount(2) syscall: source: "/dev/mapper/c-c", target: "/mnt", filesystemtype: "vfat", mountflags: -1058209792, data: (null) mount: /dev/mapper/c-c: can't read superblock

I need clarification on what's under the hood with X-Raid.
Is it simply LVM1 Striping across Multiple disks or is there "real" raid under there.
LVM2 can create raid arrays directly but what of LVM1, I believe it did not do Raid itself but relied on MDADM Raid sets to be presented as disks to become PVs
Does XRaid rely on MDADM.
I have run MDADM --examine --scan /dev/sda5 /dev/sdb5 /dev/sdc5 /dev/sdd5 but it found no raid info.
So it is not obvious what exactly XRaid is.

Can anyone give me the last couple of pieces to the jigsaw.

Thanks a mill