1940s Parker Quink with "Secret Solvent", Permanent Black, ink w/ box, see desc

Description

Vintage Quink with "Secret Solvent", Permanent Black, in box.
Ink formulated for Parker fountain pens. "Contains a secret solvent which washes the pen clean and dissolves sediment left by other inks." Not sure if this is the same as "Solv-X".
Based on the information at the Fountain Pen Love website, this appears to be from the early 1940s. The box is in good condition for its age; in fact I assumed at first that this was unopened.
However, when I opened the box, the bottle appeared to be only about 2/3 full.
The ink where it washes against the bottle appears to have left a brown stain rather than a black one; I don't know if it's supposed to do that.
I also have a vintage bottle of Skrip listed; happy to combine shipping.