So, I've been able to find sporadic references to this colour here and there but I can't find a formula. I've found a Ditzler number, 13732 but nothing more than that. It was pretty rare, maybe offered from '67-'70 if it went that far even. Here's a pic.
Failing that, does anyone know if the modern FJC colour Heritage Blue looks somewhat close in real life? Thanx folks.

Failing that, does anyone know if the modern FJC colour Heritage Blue looks somewhat close in real life? Thanx folks.