Telecasters and Esquires made between 1949 and mid-1959 featured a one-piece hard rock fretted maple neck, without any separate fingerboard.  Leo Fender never intentionally used fancy figured woods, because his instruments were designed for working musicians, although it is possible to find stunning figured maple necks on ‘50s Telecaster style guitars, especially in 1954 or 1956.
During the ‘50s, necks finishing included three coats: sealer, primer and glossy nitrocellulose clear coat.  By the late ‘60s, Fender started to use a polyester finish, which was much more durable and resistant to scratches and easier to work with.
Bone nuts were installed in the unfinished necks and slotted before the lacquering process.  Hence, they usually featured lacquer traces on the top.  Initially, the Fender factory didn’t have specialist fret files yet, and therefore the string slots were V-shaped and wide.​
The truss rod was inserted in the neck by making a longitudinal incision on the back, subsequently filled with a strip of walnut.  The characteristic look that this gave the neck of Fender guitars earned it the nickname skunk stripe.  Maple necks of the '50s could also be recognized by the small tear-shaped plug on the nut, to fill the anchoring point of the rod, nicknamed walnut plug.  Its shape and position on the headstock might not be perfectly the same for all Telecasters, because of the different templates used to route the neck. ​

The nut of a 1950 Broadcaster, Courtesy of Guitar.com

The walnt plug, Courtesy of Eddie Tatton

The skunk stripe, 1953 Esquire, Courtesy of Cesco's Corner

Slab vs Round-Lam (1960 and 1967 Telecasters, Cesco's Corner)

By mid-1959, the neck of these guitars was fitted with a thick Brazilian rosewood fretboard, probably after the complaints of some musicians or dealers who badly digested the tendency of maple fretboards to darken with the use.  Indeed, nitrocellulose used as clear coat was quite hygroscopic and adsorbs high levels of moisture.  The rosewood fretboard was milled flat on the neck, hence its slab board nickname.
With the advent of a separate rosewood fretboard the truss-rod installation was modified, because it was easier to drill the rod channel in the neck prior to glueing the fretboard.  This explains why rosewood-capped necks were devoid of the skunk stripe and of the walnut plug.
It's interesting to note that 1959-60 catalogues showed rosewood-capped Telecaster guitars with a plug above the nut.  Probably the truss-rod of the prototypes (and maybe the very first units from 1959) was still inserted from the rear and not from the front.

After July 1962, a curved rosewood fretboard, with a convex base, replaced the slab board.  At first, the rosewood cap remained fairly thick, but in 1963 it gradually turned into a thinner veneer which was kept this way until mid-1983.  Veneer fingerboards (a.k.a. round-lam) could be quickly identifiable from the headstock by their dished line toward the nut.
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1961 Stratocaster slab board

1973 Telecaster round-lam, Courtesy of Real Vintage

1968 Telecaster maple-cap, Courtesy of Real Vintage

It is common opinion that Fender switched to the round-lam fingerboard with the aim of saving the rosewood, even if, according to Dan Smith, Leo decided to use the veneer fretboard only because of the different expansion coefficient of rosewood and maple.  In fact, the two woods contract differently according to the different humidity conditions and, as this difference could determine some problems in the way the slots of the Telecaster frets were cut, Fender decided to modify the fretboard type: “On the most of slab boards, slots are cut straight across, parallel to the flat back.  They go almost all the way through, so instead of a solid hunk of wood, the effect is to have a bunch of little blocks.  When the weather changes, and the rosewood and maple expand or contract at different rates, they can twist or warp.  It's not a big problem with deep slots, because the fingerboard is more flexible and there's some ‘give.’  But Leo used a swing-arm fret slot cutter, and the slots were curved on top and not as deep, so he had this thick beam of rosewood running down the neck, and it could twist or bend with shifts in the weather; it didn't ‘give.’  He didn't want to change the way he cut slots, so he went with a thinner, curved piece of rosewood.”
In 1965, the Brazilian government, to favor local businesses, imposed an embargo on the export of Brazilian rosewood, which could no longer be exported as it was, but already partially cut into blocks.  Fender, which was not satisfied with the quality of the blocks of wood from Brazil, therefore stopped importing this wood and soon ran out of supplies, preferring the Indian rosewood.  The transition was not sharp but gradual, and it is possible to find Brazilian fingerboards dated October 1965.  Finally, the Brazilian rosewood was included in CITES protected species in the summer of 1992.
In January 1967 optional maple fingerboard were officially listed at an additional 5% cost, but maple-capped necks were produced well before 1967 on a custom order basis.  A glued-on maple board from the '60s is easily distinguished from a one-piece maple neck of the '50s by the absence of both the walnut plug above the nut and the skunk stripe on the back of the neck.  Furthermore, the original 1-piece maple neck from the '50s was sealed with clear nitrocellulose lacquer - often yellowed with age - whilst the post-69 version was finished with polyester.  From a purist’s point of view, they should not be referred to as “maple necks” (which somehow implies the notion of a one-piece neck), but as maple board or maple-cap necks.
In early 1969 the original one-piece fretted maple neck was reinstated as an option in lieu of the maple cap board.  By then, in order to optimize production, Fender decided to insert the truss rod from the rear of the rosewood-capped necks, too.  This is why Telecasters made after Spring 1969 usually featured the skunk stripe and the walnut plug above the nut.

PIN ROUTER'S HOLES

From '50s until late '70s, Fender used a pin router and templates to cut guitars neck edges.  Routing templates had locating pins to secure them onto the underside of the neck blanks.  Then, when the template was removed, two small holes always located on the back of the headstock, between the holes drilled for the D and G tuners, and underneath the neck's heel were left.  

A worker Shaping an headstock with a router, 1952. Photo from “Fender, The sound heard 'round the world” by Richard R. Smith

Pin router's hole, back of the headstock. Courtesy of Real Vintage

Pin router's hole, neck heel. Courtesy of Real Vintage

Position Markers

Black Dot detail, Courtesy of Eddie Tatton

The snake head prototype and the original neck of the second prototype featured small painted dots.
'50s 1-piece maple necks made after March 1950 were inlaid with 0.25 inches wide black dots.  Originally they showed a 5/8" spacing at the 12th fret, but, in December 1952, the 12th fret spacing was widened by 3/16" and the double dots became neatly crossed by the A and B strings.
1959 rosewood-capped necks were initially inlaid with matt white dots, which often over time tended to turn yellow and become light brown, that today are known with the term paper dots or, more frequently, clay dots.  

Being composed by a fibrous material (that, analyzed in the laboratory, turned out to be mainly made up of zinc hydrochloride and cellulose), and not by a pasta called ‘ivorina’, as sometimes erroneously reported, they were inserted in the fretboard as discs only 0.0625 inches tall, so thin that, during refrets, they could even jump off.  It appears that some of the very first fret-markers used on rosewood boards were composed by a flax fiber.
Clay dots initially kept the same 12th fret spacing as the post-52 maple necks.  But, after mid-1963, the 12th fret dots were moved closer to each other again to the original 5/8" narrower spacing, whether on rosewood or maple-capped necks.
In early 1965, clay dots were replaced by slightly bigger pearloid dots, which kept the narrow spacing at the 12th fret.  These pearloid dots became a standard appointment on rosewood-capped necks until mid-1983.
By mid-1983, pearloid dots have been discontinued and the new rosewood slab fretboard was inlaid with matt white dots, which kept the narrow spacing at the 12th fret. This combination was still a standard trim on the American Standard Telecaster officially introduced at 1988 Winter NAMM.
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1950 Broadcaster, narrow spacing. Courtesy of Cesco's Corner

1953 Telecaster, wide spacing. Courtesy of Cesco's Corner

Black dots fitting at Fender: they were discs pressed into the holes and not a paste scraped into the hole.

Clay dots fitting at Fender: they were discs pressed into the holes and not a paste scraped into the hole.

Clay vs pearloid dots

Side dots on the upper edge of the neck also changed over the years.  In the '60s, they were black on maple necks and whitish on rosewood-capped necks.  On the latter, the side dots generally sit astride board and neck, with the exception of the Telecasters made since late '71, which featured side dots inlaid into the neck, apart from the fretboard.

'60s Fender guitars featured side dots set astride fingerboard and neck

'70s Fender guitars featured side dots inlaid into the neck, apart from the fretboard

Mounting Screws

In the early days, Leo Fender bought the screws from readily available stock, and therefore he used many different types of screws on prototypes and pre-production guitars.
All the 1950 Telecaster-style guitars featured slot heads, including the adjustable truss rod bolt.  In 1951, Fender started a gradual transition towards Phillips heads screws, but the transition was completed by the end of 1953, because Leo Fender didn’t want to waste anything.
In the course of 1951, the truss-rod bolt and the screws fastening the neck changed to Phillips heads.

Notes

In the early '60s a few Telecasters featured a cocobolo fretboard in lieu of rosewood and hickory was also occasionally used for necks instead of maple.
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Other Models

Production Rosewood Telecasters were made with a one-piece rosewood neck.
During the '70s, Custom Telecasters could be ordered with either a rosewood fretboard or a maple neck, but the Deluxe and the second version of the Thinline were exclusively fitted with a maple neck.
The 1983 Walnut Elite Telecaster featured an ebony fretboard.