Rega Origin Tonearm (?)

Can anyone help me identify this odd bird?  I've looked at photos on line, and can't find an exact match.  It's very close to the Origin Mk I and MK II, but not identical.  Different drill pattern for cart mount, etc.  Also has a custom heavy counterweight. 
https://photos.google.com/share/AF1QipN2ux-yw4xJLLpvvtjdlkz6AceIhK486eoKNXqmqDv6Bxnir8jRUN9Uf6BFeb87KA?key=RmQxcl9LemRERnVfMFBBeXE5allxRjlIN01QNDZR