Size of the Didot point

[Member Emo…]

If you encountered a measure given in Didot points (‘dd’ for brevity) and the exact age and origin of the source was unknown, which conversion factor would you probably choose?

• 15 dd = 16 pt (Anglo-centric)

  • 1 pt := 351.4 µm (JIS)
    ⇒ 1 dd = 374.82(6) µm

  • 72.27 pt ≈ 1 in 
    ⇒ 1 dd ≈ 374.890 µm

  • 72 pt := 1 in
    ⇒ 1 dd = 376.(296) µm

• 8 dd = 3 mm ⇔ 2 dd = 3 Q
  ⇒ 1 dd = 375 µm (DIN nominal)

• 864 dd = 1 pois du roi ⇔ 72 dd = 1 pouce du roi ⇔ 1 dd = 2 tp (Truchet)

  • 133 dd := 5 cm
    ⇒ 1 dd ≈ 375.93985 µm (Berthold)

  • 41559 dd = 15625 mm
    ⇒ 1 dd ≈ 375.971510 µm (revolutionary France)

• 1 dd := 376 µm

• 1 dd := 376.065 µm (DIN)

• 11 dd = 12 fp (Fournier)
  ⇒ 1 dd ≈ 376.26 µm

• 1 dd := 0.01483 in = 376.682 µm

• 12 dd = 1 cc := 0.178 in 
  ⇒ 1 dd = 376.7(6) µm

[Ralf Herrmann]

The context would define what probably works best. I can’t imagine a situation where there would be absolutely no context given.