Heres a brief description of 1960-1966 15 inch wheels.
Starting with 1960 and two different styles of rims for that year. One is a Kelsey Hayes , the other is an NT wheel for Norris Technology's. Both have no bead lock , Both have different center hub profile. Bead lock 15 inch rims started around 1964-1965. 5/8 valve stem hole and 3 hubcap clips and the size is 15x5 . They also have 4 nubs around the OUTER edge for full wheel covers.
1961 , the introduction of the 3 nub 15x5 , I only have this one style NT wheel to show off my brothers 61 shorty. It is dated 1961 but for some reason still has the 4 outer rim nubs for full wheel covers. Possibly an early design. I have seen dated 1961 wheels without the 4 nubs. Not to be confused with the 3 nubs for Dog Dish style hubcaps.
1962-1963-1964 Wheels. Still 15x5 width, 5/8 valve stem hole, 3 nubs ,no bead lock. Kelsey hays style. Notice all of these wheels in this post are dated although Im missing 62.
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1965 and 1966 wheels. Here starts the bead lock rim AND the 15x5.5 NT and 15x5 1/2 KH markings AND the smaller Valve stem hole of 1/2 inch as compared to the 5/8 hole for 1960-1964 rims .I do believe theres some overlap with 1964 on this style rim.
This last picture , my thumb is pointing to a 1963 NO bead lock edge, on the far left 1966 rim you can see the indentation of the 65-66 bead lock rim.
Theres still more details Id like to add and other versions to add to this group of 15 inch wheels but I just don't have the time at the moment. I have the part numbers to go with these , will add at a later date. 16s will be next. Note on 16 inch and up wheels , they all had the larger 5/8 valve stem hole.