The value of pipe #688 is n/a points.
Sal Vitello came across this very rare Venturi with a pyrolytic graphite bowl liner! Suddenly there have been three of these turn up. I checked with a local plastics manufacturer and was told that the technique for over-stamping on the plastic requires the right equipment and know-how, but isn't terribly difficult. Just heat up the plastic, position a new stamp and WHAM! My best thinking at the moment is that, after the trademark the pipe went to the Falcon Group in England, it may be that Bissell felt constrained to overprint the logo with the one they had bought rights to. This is rank speculation on my part, there may be some other explanation entirely. I'm not even sure how to classify this pipe; it is marked Venturi, but clearly as an over-stamp. And it has a pyrolytic graphite bowl liner which makes it a the pipe. For now it is carried as a variation of Venturi, but that's subject to change. As I said, it's a rare thing. I have not assigned a point value to these pipes until we have more information.