The making of the 3 Piece Dials:
Step by step history guide to the Vintage Panerai 3 Piece Dial
1) Many 3 Piece Dials are not 2mm thick
2) The indices (numbers) do not have a Plexi
3) Indices (numbers) on the 3646 and 6152 dials were not the same
4) Engraving had more than one font type on the same dial!
How were the dials made?
The dials started life by being turned from a solid bar of aluminium on a simple lathe. Each dial was "faced off" flat across the front then turned and shaped on the back. The alloy dial at this stage would have no numbers. The 3646 dials were made differently to the 6152 dials (see below).
The 6152 Dials were no thicker than 1.5mm. This gave greater hand clearance but it also meant that the tall Sub-Dial Hand Staff still had to be quite tall. However, no special Cannon Pinion or Hour Hand was required. The height of the Hour Wheel was 3.5mm tall. Angelus also made an Hour Wheel 3.75 tall but this wasn't used on the Vintage Panerai 6152 (the 3.5 Hour wheel was ample). The 3646 dials varied in thickness from 1.8mm, 2.00mm and 2.40mm, all movements for the 3646 required a Tall Cannon Pinion and Hour Wheel.
3646 Dials: Once the lathe work was finished the blank dial (no numbers) would then go to the Pantograph Operator who would cut each number into the dial using a Template which he/she followed by hand. The next stage would be to engrave the Panerai Logo. Early dials had no logo, later dials (1940 -1950's) had Radiomir Panerai engraved. Again this work was done by hand on the Pantograph. However, not all fonts were identical often the same dial had two different fonts! (see further explanation below).
6152 Dials: The procedure for these dials probably changed around the early 1950's (maybe late 40's) evidence of this can be seen on the 6152 dials. Instead of the dial being engraved directly onto a blank aluminium plate Panerai decided to anodize the dial first, then engrave after anodizing. This is evident when viewing the 6152 Militare Marine or Luminor Panerai dials. If you look closely around the numbers you can see bare metal. This is were the Pantograph Operator has cut into the surface of the anodized dial. In short the operator was given a fully anodized dial to cut both the numbers and also the engraved text (logo).
Dial Number Colours (basic rule).
People often assume all Vintage Panerai dial numbers are discoloured (aged). Whilst this was true for the 3646 watches, this rule does not apply to the later 6152 watches. Many Panerai 6152 watches kept fairly white indices (numbers). Dial or number colours were probably affected by the lume or radium (radioactive luminous material) within the lume (plus age)
1) 3646 Sterile Mainly Red due to age and radium within the lume
2) RP (3646) mainly Yellow-ish/orange colour depending on age
3) MM - LP etc Mainly white.
The surface of the authentic dials were textured (not smooth). The reason for this was to remove the machining marks. Its possible Panerai used an air tool to treat the surface of the dial. This did two things A) it cleaned the dial of machining marks and B) it also reduce the shine on the surface of the dial which may have been an important factor when viewed through a Plexi glass. Its possible Panerai wanted to achieve a semi/matt or non shiny finish.
Below: microscope image of the surface of the dial
It has been wrongly assumed by some that Panerai added a Plexi to the dial that formed the shape of the numbers and protruded from inside the dial so that the Plexi could be viewed from the outside or surface of the dial. This is probably "not" correct. Whilst Panerai did add a Plexi to their dials, the plexi was in the centre of the dial and is not visible once the dial is assembled. The purpose of the Plexi is to hold the lume.
Causes of cracking: Its unknown whether this was caused by the type or resin used, radium or whether some watches were issued to hot countries (climate) and exposed to higher levels of sun or heat.
3646: fewer resin cracks but the resin aged and discoloured
6152: many cracked over time yet stayed clear and opaque
What are dial the numbers made of? Panerai probably finished the numbers by hand using resin to fill each number. Each number is flush (level) with the surface of the dial. The resin would be left to set hard, if you look carefully on some authentic images you can see the odd tiny air bubble that should not have been there (suggests a hand mix and application).
About the Plexi? You should not be able to see a Plexi on a genuine Panerai 3 Piece dial. This is because the plexi is in the middle of the dial. The purpose of the plexi was to hold the lume. Plexis were made using a Pantograph Machine. Once the Plexi was machined on a lathe to size it would then be clamped into a jig and a recess for each number was cut by hand on the Pantograph Machine. The Plexi would then be passed to people that would apply the lume and then later it would be inserted into the centre of the dial.
Engraving was done by Pantograph (hand operated). If you look carefully on early Panerai dials particularly the 3646 you will see that there are two letter "R's" yet each letter is different, was this an error? To understand let's focus our attention on the Pantograph. In order to engrave the word "Panerai Radiomir" the Pantograph operator has to follow a large hand-made template. Each letter will have been cut into a template, it appears they didn't get the letter "R" the same. Was this deliberate or error? My guess is that one letter may have been stretched a little so that the upper and lower words "Radiomir Panerai" align together. Radiomir contains 8 letters and Panerai 7 letters the "R" in Panerai may have been made wider so that both words align equally.
Other Engraving anomalies: If you look carefully at many Vintage Panerai dials (common on the 6152) you will find the engraved letters are not always precise. This is caused by the Pantograph operator and/or cutting tool. A Pantograph operator will control the direction of the cutting tool he/she will also control the height as well. This means some letters were thicker or thinner than others due to the height or thickness of the cutting tool.
The backing plates were made of brass and the dial feet made of copper or brass depending on dial type. The dial feet were hand soldered and then the plates were nickel plated. On some dials there are circular machine marks around the base of the dial feet. Was this to clean the burrs after drilling or was it the result of the drill chuck touching the dial surface? The 6152 varied (depending on movement type), some had one copper or brass dial foot that was solid and one that was threaded, very few had both dial feet threaded internally yet there were some that had both feet as solid copper as well as brass, quite a mixture. Angelus 240 cal movement (mar-juni 61)hole locations were not always the same as the hole locations used on the Angelus 240 cal clock.
Other Odd or unusual points:
When all parts of the dials were assembled it was very important that the back of the dial (backing plate) is aligned flush (perfectly level or flat) with the front dial plate. Occasionally when the backing plate was added it would sit too low. To compensate or lift the backing plate slightly Panerai would add a layer of Silver Paper or foil.
Below: Resin Indices and lume, note how its impossible to see the Plexi
Below: The clarity of the resin is still super clear even after many years
Below: Possibly a 2mm thick 3646 Dial on a Rolex 618 movement. Other sizes were 1.8mm, and 2.40. Whatever dial Panerai used on the 3646 then a Tall cannon Pinion and Hour Wheel had to be used.