Jowo 6 Nib Unit | Waterman's | #5 Ideal Keyhole | 14kt Gold | Fine Flex

🥇 Grade: B+
🏠 Housing: Nikko Red Ebonite, JOWO #6
🔱 Nib: Waterman's Ideal Reg. U.S. Pat. Off. Made in U.S.A. 5
🖋️ Line Spec: F – 3B | 0.30mm – 1.23mm (4.10x)
🌡️ Flexibility Pressure: 370g Flex
📐 Dimensions: 21.38mm nib length past housing
⚖️ Weight: 1.917g

A keyhole #5 with a proper fine hairline and a 4x swell. Unflexed it's 0.30mm in both directions, so plain handwriting comes out as an even fine line with no stub character, and with moderate pressure the tines open to 1.13mm on a straight downstroke and about 1.23mm at the top of a flourish, a 3B. You need a bit of pressure to get there (it sits in the Flex tier, not the softer ones), which for most folks means it writes fast without the tines wandering.

The stamp is Waterman's Ideal Reg. U.S. Pat. Off. Made in U.S.A. with "Ideal" being the trademark, in use since 1904. The keyhole vent came in with the No. 7 in 1927 and the No. 5 in 1928, when the nibs were graded by color and stamped with the color name; the No. 5 pen was gone by about 1934 and the color names dropped off the stamps by the late 1930s, so a keyhole #5 with no color on it generally dates to the mid to late 1930s, after the colorband models.

I've rated this B+, gold bright with only slight use, imprint legible, tines even and original, tipping intact. Tines aligned, tipping smoothed and polished, and the nib heat-set to a matched red Nikko ebonite feed in the JOWO #6 housing, then tuned and written in as a set unit.

Tested on Tomoe River 68gsm White with Pelikan 4001 Brilliant Black.