I have an original unrestored tank, from a twin my father bought new. The scroll transfers vary by 1/2 an inch vertically from side to side, but are close to where the "Throwing Light On Obscure Objects" MPH article says they should be, and the mercury crest is exactly where that article says it should be, which is closer to the seat than most people nowadays put it. I admit, to me, the mercury crest looks better where most people put it, but it appears that that was not how it was typically done by the factory. If and when I ever restore it, I will put all three transfers exactly where they are now, replicating the offset the scrolls have. But that is one specific tank.
My Comet tank was recently done, and I hadn't yet seen (or actually, remembered) the article, so I did not tell the painter where the transfers should be, and the scrolls came out very close to the spec, but the mercury crest is closer to the oil filler, like most restorations, and that is fine.
Don't even get me started on which mercury crest a given bike should have. A famous restorer in LA puts the Vincent Engineers version on just about all Series Cs, despite my telling him very few Cs should have that version. At the end of 1952, bikes in the high 98xx range were being built and road tested. When did the factory adopt the Vincent Engineers name? Do the math to figure out how many Cs should have that transfer.
As for the font etc. used in some repro transfers, the VOC found some documented old stock original transfers, and had new artwork done. The transfers now available from the Spares Company are true to the original transfers. The various repros over the years had indeed strayed noticeably from the originals.