OK, so this is a BT4, not a BT8. I am stupid and have caused myself and the guy interested some problems.
So, here it is folks, a Hipshot BT4! Unhelpfully this isn't listed on the Hipshot website (one reason for my error), but Bestbassgear has this to say -
'The BT4 fits - American-made Fender '82-'84's, '90 and newer Elit's, P-Bass+ and J-Bass+, American Standard Jazz, and Deluxe P-Bass+ with thin stamped cloverleaf key.'
Whatever that means.
[url="http://www.bestbassgear.com/hipshot-bt4-bass-xtender.htm"]http://www.bestbassgear.com/hipshot-bt4-bass-xtender.htm[/url]