I may have worded it wrong . I played a custom shop’59 esquire with the large c . There definitely is other models from fender of the same year with a smaller c shape . I don’t know why that is . I assume most were the large shape before 1960, then they for the most part , got skinny . My 63 custom shop had a very skinny c shape , like .79”
Here's my admittedly limited understanding:
In general, historically, and borne out in many (but not all) reissues, the 50s began with the big U (though at that time each neck really was a bit unique).
In October 1956 (10/56), enter the chunky soft V. The perfect neck, IMO.
By some time in 58 the transition had begun, and necks skinnied down. When was it a C? Dunno. Very subjective, those shape letters. My AV58 doesn't feel at all like a C to me. More like a smaller U. Fender calls it a D.
In the early 60s, necks were downright skinny.
But then around 1964 necks grew once more, into a fairly large oval C. Not really that big, but miles different from the modern C.
That's my understanding. It's largely borne out by looking at some of my guitars, too.
2015 AV 52 Tele: .92 / 1.02
CS 57 Strat: .87 / 1.02
AV 58 Tele: .84 / .96 (getting smaller now...)
2009 AVRI 62 Telecaster Custom: .82 / .91 (skinny!)
AV 64 Tele: .87 / 1.00 (It's nearly the same as the 57. It seems smaller, but it plays similarly, even though it's an oval C, not a V)