One is a pre-label, lightning throw, hex nuts inside.One is a labeled, lightning throw, flat head screws.One is a removed label, flat head screws, Supersensitive throw.The last snare has no lines in the middle, those small little marks in the middle of the snare, the other 2 have those lines, this one doesn't...? Why?????
From what I can tell, the earliest of the Model 4160 snares had no central knurling lines, a microsensitive throw and round/flat head screws (not hex) holding on the lug casings. The first thing to change was the knurling. This happened in the mid 60s. Note that catalog #43 (1966) shows non-knurled shell Model 4160 snare drums on the cover, page 3 and page 5, but a knurled shell on page 8.
Next was a change from microsensitive to lightning throws in the later 60s.
Finally, slightly after the throw was changed, the lug mounting screws changed from the round/flat head to hex heads.
Based upon the above progression, I would put your drums in the following order, oldest to newest - 3, 2, 1. (It appears to me that you describe 3 drums, even though at one point your said there were 4. Let me know if that is incorrect.)
Your "pre-label" drum was probably made during the label era and did not receive a label or it fell off without leaving much of a trace that it had been on there. This is not uncommon for the chrome snares.
Can you tell me if the serial number on the one drum that has a label (knurling, round/flat head screws and lightning throw) is in the 85000-95000 range? That would be consistent with the information that I have gathered.
Rick