Variations of S6 valves

[Doug]

I wonder if someone can help with identification of some S6 valves. I seem to have an assortment of a few various sizes.

Sample    Quant.     Ø Head    Ø Stem     Comments
1              1              1.687       0.342       Presumed to be S6
2              1              1.639       0.342       ditto, but undersized head
3              1              1.602       0.339       S5?
4              1              1.587       0.339       Ditto
5              2              1.567       0.372       Large stem, industrial?
6              3              1.752       0.340       Large head, 1934-35 750cc?

I am guessing the first two (1, 2) are the definitive S6. They seem to be of the proper head diameter to suit the cylinders I have on hand. (3, 4) I am guessing are for the S5/C31 since the spares list indicates they used a different valve by part number. Since all share a common valve guide according to the spares list, I know (5) can not be for the S5. I am guessing it might be for one of the industrial engines that used the S6 derivative, but I have no way of verifying. Another curiosity is (6), with the large diameter heads. Again, taking a wild guess that perhaps on the last 750cc iteration of 1934-35 (Powerflow) they may have enlarged the valves. It would be interesting to know, as these are new-old stock. They could be turned down to S6 spec, but it would be a pity for someone that had a Powerflow and needed the larger valves. Not so easy to put the metal back on! Any thoughts on the above?

-Doug