Steve, wow...have not discussed these putters in years! 

They were primarily produced in the late 90's for a few years and the rubber gasket is actually called elastomer in the color of white.  The copper insert with the white elastomer provided a muted sound which is why it sound/feels softer.  These gave way to newer inserts such as the button back line along with other types of inserts that work to increase the MOI as well as different types of millings on the face on the putter such as light, medium and deep.

At the end of the day, they are "old" technology and the market has surpassed them however every once in a while these pop up on tour but not very often.  They also had a very think topline and more current models have a much thicker topline which most players prefer in the 009 and Tour Rat made for tour models.

Just some random thoughts, hope I answered your question!

That is an interesting point about the elastomer.  I was told by another collector that the non-elastomer teryliums were more valuable because the tolerances needed for the terylium insert were much more specific.  Whereas the elastomer allowed for some margin of error.

Any truth to that?

To add to what Chris said they were made from 1997 - 2001 and the models were Newport, Newport Long Neck, Newport 2, Newport 2 Long Neck, Santa Fe, Santa Fe Sole Stamp, Delmar 2 mid slant, Limited Long Slant, Xperimenetal Prototypes and I'm sure that I left some out. I have a friend that uses one and he can really putt with this stick and he takes really good care of it so it still looks great.

I used to game my Longneck but have since stopped and made it a shelf rat. Love the design and feel from it, probably going to hang onto her for a while. 

Steve, I have one of the limited edition Cameron button backs with the Terylium insert and it can't be beat.  I absolutely LOVE the way the PROV ball kisses it's face is pure bliss.  Happy holidays!