Dagnabbit, it's the month of gypos. I mean typos. AdMES and ORdA are not words.
Our theme today is a pair of the same numbers separated by a forward-slash, with each example interpreted in a different way. Thus, 4/4 is COMMONTIME, a musical notation often represented with a C in the score (for the above phrase). 11/11 is a date, namely VETERANSDAY.
Then it starts getting iffy. 20/20 is interpreted as GREATVISION. I think the term typically used is "perfect vision," although if that's perfect, what was Ted Williams's 20/10? In reality, what it means is that you can see at 20 feet what you should be able to see at 20 feet. An eye with 20/50 vision sees letters at 20 feet as if they were 50 feet away, thus with less acuity.
Worse, in my mind is the answer for 50/50 (EVENSTEVEN). Huh? That's "even odds," I suppose. Google defines "even steven" as being a fair or equal distribution of resources, so in one sense I suppose 50/50 means that. But to me, "even steven" means that you've come out neither ahead nor behind. Or that in a race, two competitors are neck and neck. I don't see how that means 50/50. I call foul.
Are there other examples of this theme? I'm rather fond of 3/3, as it's my birthday, but a date's already been used.
Outside of the theme, there's the humorous 10D: Something that gives you a sinking feeling (QUICKSAND). The other long downs are also strong, especially PRIMEVAL and the appropriately downward moving NAMEDROP.
Perhaps 40D should have been clued "One of over 200 by Edna St. Vincent Millay." Put that in your pipe and smoke on it, Mr. William so-called Shakespeare!
1A: Row (SPAT). C. It's so perfectly average.
Fave: SADIE (63A: "Sexy" woman in a Beatles song). This song has a similar chord progression to "Karma Police" by Radiohead.
Least fave: ACMES (3D: Zeniths). Not because I typoed it, but because how many highest points can there be? LENTS was a close second.
I think I liked this puzzle okay, despite my disappointment in the theme.