Well, no definitive answer I'm afraid, but here's what the TT2 lads have come up with so far.
Roy Thersby
That is a remote resevour adaptor in a brembo master cyclinder, i made them and for other master cyclinders in the 1980's we made both clutch and brake Ducati followed by making them standard on certain bikes
Dean Brown
Thanks for that, Roy. Is it one of yours then or an example of a common mod from the time?
Stephen Hay
looks like it is off a BIMOTA DB1, I have one and the reservoirs for the front brake and clutch are remote from the master, linked by a length of hose
Dean Brown
Great minds think alike Stephen, someone has also suggested a Bimota connection on the Laverda site. "Bimota DB1 used that type of setup with the remote reservoir conversion, but they were normal black ones and I don't know what size they were."
Roy Thersby
Its hatd to say the first ones were just billet plugs tapped and a machine groove placed in the side of the disc to accomidate the sealing o ring the idea was the reservoir caught the tt2 screens and caused a problem adjusting the clipons for different riders. It could be on I made over a 100 of them also for honda and yamaha m/c as brembo hadnt got their sizes correct for different callipers and the jap ones were a ?100 cheaper. To replace if a tumble off occured. I think a charged around a fiver a time for them.