I received an answer from Midwest:
As far as I can find, the ones we get ( from LD Carlson ) are "NOMACORC 9 X 1 1/2 SELECT 900 SERIES CORKS". I saw the various ones on the Nomacorc site, those seem to be even higher-grade than the ones we have always carried. The ones we sell are good for longer than most folks would ever need, easily 5+ years
BTW -- I give Midwest high marks for the speed of their shipping process and the return time in responding to questions.
There is no "Select 900" listed on the web site I mentioned in the last post. However, LD Carlson lists it as the same name (which is where I expect Midwest got it from). I found another site that said the Select 900 replaces the Classic series -- which the info sheet says is good up to 5 years. This doesn't give me warm fuzzies.
I hit the Nomacorc site -- the Classic series is presented as a good medium term solution (my description, not theirs). They present a lot of information without saying much. I submitted a request for samples -- not sure I'll get anything, but it's worth a shot.
Another BTW -- they are located in Zebulon, NC, about 20 miles from me.