>>41337412 (OP)
not a fed but its mostly smoke an mirrors as far as I can tell. Did a deep dive into reproducing them and as far as I can tell the spectrographic response given by a dicyanin screen of alcoholised solution between two panes of glass can be replicated .
Now the fluid nature of the screen may matter, but unless you know more about spectrography than me Im not sure why you haven't just refined your own coal tar. I've thought about asking a local chem student to do it for me as I dont have lab equipmetn and an alembic is expensive.