This is for a 1940's waterman nurse's pen. Flexes nicely to 2.46mm (it was set to inches in the picture). These were marketed to nurses. Finding one that is not heavily discolored is rare.
The nib produces a nice fine line but still flexes well past 2mm. This pen is extremely fun to play with. I have enjoyed using it to take notes, and still have fun with ornamental writing in the margins. I wish i could say this is full flex, it is so close.But it comes in at a 6mfs (5 or under is full flex). Please review the pictures carefully, they are part of the description. My goal is to restore these pens to the best working order they can. 0 -wet noodle (brause rose nib for comparison) - takes practice to not flex on the downstroke, can be temperamental. 1- wet noodle (leonardt principal maybe)- takes a light hand to use correctly. The slightest pressure opens the tines. 2-5 full flex with a 2 being very easy to flex and a 5 taking a bit of intent (but not much pressure). 6 the start of semi-flex.
Slightly more difficult to use with continuous flex (every downstroke) and takes some pressure to get it to fully flex. 7- continuous flex becomes hard around curves (suitable for spencerian). 8 - continuous flex becomes very difficult. Many pens from the 50's have this lousy flex.
Only good for accenting cursive with some minor shading. I only have a very few of these for sale.
Might produce very minor line variation with heavy pressure. I don't sell nails atm but if i do, it will come with a warning. In my humble opinion: anything under a 4mfs with enough width is acceptable for use with copperplate. Anything under a 7 but above a 2 is suitable for spencerian w/ shades.Anything under a 5 but above a 2 is suitable for many ornamental scripts w/ shades. I will however work with you to get the most out of your pen.