Pryso, I had both a MkII and a Mk2A for a while. You are quite correct; there is a difference between the rubber mats supplied for those two tts. The MkII mat has those fine concentric rings, as you say, and may be more flexible, made of less rigid or thinner rubber, compared to the 2A mat. The Mk2A mat resembles, if it is not identical to, the rubber mat supplied with the Mk3. (I also have the correct original mat for my Mk3; it is not warped, but I expect to be using something more like the SAEC, based on my listening tests with the Mk2A and DP80.) Problem is also that my Mk2A mat is NOS, was never used and therefore warped a bit during storage. There must be a way to flatten it, but that is what motivated me to shell out money for the SAEC mat, which came highly recommended by Raul.
John, This business of piling one mat upon another seems a bit odd to me, unless it is to build up the mass to match that of the stock rubber mat, which is a good idea. I really like the Boston Audio Mat 1 on my Lenco, but it is way too light to use by itself on a Technics, due to possible effects on the servo.