Capped - Parker 51 is slightly longer and wider
Posted - Both pens are about the same length
Both caps are 14kt gold filled with thin lines closely spaced. The Lamy does have a slight variation on line spacing. In each case, there is a jewel/accent that secures the clip (the Lamy clip penetrates the cap, but the Parker clip rests on top). Both caps are slip on, secured by a clutch ring.
The Parker 51 features the vacumatic type with blind cap covered plunger. The Lamy 27 has an internal piston, controlled by the barrel screw tip. As you can see in the photo, the Lamy has a series of ink windows near the clutch ring, so you can easily see how much ink is left.
Unlike the Parker 51 hooded nib, the Lamy 27 nib is mostly exposed. The Lamy nib is integrated in the section--the whole piece easily unscrews from the barrel.
On the 27, Lamy usually imprints the model number (27n) and nib type (OM) on the piston screw tip, as well as "Lamy 27" midway on the barrel (pens made specifically for export to the US have different markings). The early Parker 51's have the model and date code on the barrel near the clutch ring.
Edited by MYU, 08 May 2007 - 18:05.