Naphthalene Blue Black
Lendrum used this dye for the demonstration of fibrin in his Masson 44/41 and Obadiah methods. He considered that it demonstrated the oldest fibrin at a stage when it was not distinguishable from collagen by any other staining method.
The dye is not easily available, and not used in any other procedures than Lendrum's Masson 44/41 and Obadiah, both for old fibrin. Naphthol blue black, otherwise known as amido black 10B, CI 20470, is closely related and may be a suitable substitute. Compare the formulae of both dyes.
Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.
Colour Index, Ed. 2, v. 3 (1956)
Society of dyers and Colourists, London, England.