How do I trace an FGP lot number back to a synthesis date?

The lot number on the vial matches the certificate, which at least rules out the easy problem.

This is a procedural question rather than a theoretical one, and I would like the procedure rather than the theory.

What I have done so far is read the label documentation where it exists and the two pharmacopoeial monographs that are publicly available, which cover the licensed presentation and say nothing about a research one.

What does a defensible version of this look like in practice?