TT mats

I'd favor Delrin over acrylic, for no good reason.  Just a "feeling" combined with the fact that I am not a fan of acrylic platters to begin with.

@bdp24 I had a TNT Mark III with the original platter and switch to a classic platter. I ran both with no mats. I find the classic platter to be more live sounding, a little more dynamic with perhaps a touch hotter treble. I do think preference has a bit to do with your synergy with your cartridge.

@analogluvr , good point. I use rather "lively" cartridges (London), and I’m thinking the Classic/London combo may sound a tad brash. London’s create a lot of mechanical energy, and a platter surface that is very hard (aluminum) may reflect it back rather than damp it a little. That’s the theory, anyway! The folks at the plastics place told me Delrin is harder than acrylic, for what it's worth. Also denser and heavier.

bdp24, That's the crux of the matter, when it comes to platter mats, the transmission, or lack thereof, of energy between the LP and the platter.  Do you want that or don't you want that?  Each of us has to answer that question "by ear". If you want that, you use a platter mat that is similar in material construction to an LP, then you clamp the LP, and you might also use a peripheral ring and/or vacuum hold-down, if the TT permits. If you don't want that, use a Resomat or one of those with cork dots on it, no weight or clamp, no peripheral ring.  Most tune by ear using a combination of energy absorbing and energy reflecting techniques.

Holy Moly!
I never realised there was nearly as much science in the platter mat as in the whole TT itself!
Now I am going to have to experiment!
Been using an Achromat 3mm for a while and cant say  as ever thought to experiment but.....
As an aside I could only find a couple of examples online of the SAEC SS-300 and these were in Japan and about $420.   Eek!