Fascinating coin, fascinating lighthouse. Congrats on a great pickup. It is jarring to the mind when you see something like the lighthouse in relation to a preconceived idea of how primitive the ancient world must have been.
I have not looked into the scholarship on this, but I would find use of naphtha fuel in the lighthouse to be very plausible; the ancients had some knowledge of petroleum. At the time of its construction the Pharos was one of the three tallest structures in the world, behind only the larger pyramids. It was the tallest non-pyramidal structure. Depending on exactly how high it was, it may have held that title for a thousand years.
I never thought I'd ever see a Flavian Pharos in my collection. Personally, it is an astounding coin to have acquired. And just to show how long I've been pining away for one, here is the much younger me inquiring about the type in 2004. https://www.forumancientcoins.com/board/index.php?topic=9392.0 17 years in the making.
The coin came with this curious old tag. If anyone has any info on the provenance I would love to know about it!
I believe the most easily obtained Pharos is the tetradrachm of Commodus with a ship sailing by. As with the Isis coin, the light is reduced to fit on the coin. The concept of things being scaled to size was not of high importance then.
Assuming that M. stands for Milne, if someone has both the 1933 and 1971 editions they could check them for you to see if the number matches either or both editions. If it matches only the first, then you'll know that the reference was written before 1971. If it matches both, then that fact isn't very useful. If it matches neither, I don't know what to tell you!
Wow David, you waited a while to land that one. A truly important addition to your collection. On top of that...it is a Pharos! Who would not love one?