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The inconsistency ("continuum" of qualities) @cladking mentions may show that there was little quality control for SMS in 1965. Did this continue into 1966? If 1966 are consistent, then if one compares the surface qualities of 1966 SMS to 1965, what % are similar?
Quality control was not extremely good on the SMS coins. Much of the variation resulted from using several different methods for planchets and die preparation. Some dies were hubbed differently and some were basined. Die pressure appears to have varied as well. Some planchets were polished.
The mint was trying to produce a set that appealed to both mint set and proof set collectors but these never were liked by anybody. They did a lot of experimentation trying to get just the right look. There were letters to the editor that said the sets were nearly perfect and some that said they were awful. They may have all been right.
The '66 sets were even worse in terms of different appearances. You just never knew what you'd see in these. There were quarters in this date that looked polished and were flatly struck but tended to be flawless. I've seen other specimens that appear to be fully proof.
The mint mostly settled on a single appearance in the '67 sets which almost all look a lot like proofs but much less well made. Apparently these weren't liked either because mintages dropped even further.
Mint set collectors avoided these sets because they looked too much like proof sets and proof set collectors avoided them because they looked too much like mint sets. Nobody liked them much and attrition has been extremely high on them. Most '65 sets have a lot of haze or tarnish and the others are very little better.
If you don't like an SMS coin just keep looking because there will probably be one you do like.
Time don't fly, it bounds and leaps.