I have been meaning to make this for some time. A chronological composite of David Bowie signatures from the mid 70's on to 2015. It is not as complete or neat as I'd like (not enough of earlier material for one) and I will add more observations regarding the signatures, but they are genuine and it does manage to show the evolution from C. 1976 on through the decades. There are scans and photographs of signed albums, album pages, playbills, IP, business cards, inserts, lithographs, books, scraps, photos, cards and a guitar. Various markers, pens and pencil. There are "open" and "closed" B' examples and some bits of handwriting also. I hope it is useful to you. The forgeries out there are largely of very poor quality, and usually fail from a lack of understanding regarding angle, basic construction and form. These examples are almost all dated. My favorites, oddly, are the 1983, 1993, 2003 and 2013 examples. The first 1993 example (with "open B") is in my collection and I like it because it appears a bit of a throwback in form and with that "o", and the bottom of the "B" looks like an axe blade. Comments and additions welcome. Click to see full image.
I did not just write this now - I am repairing a typo that would cause confusion made on 1/18/18.
I wanted to post this here for reference. I am copying my earlier comments from another thread for use here.
I can see how the LP on the right can appear something closer at a quick glance. Overall it has many problems. It is too bouncy and curvy, lacking the spidery straighter letters Bowie generally produced in his handwriting. The "h" in "with" - angles vs humps. Baselines, formations, all those tight curves at the start of that "B" and the creation of the "owie" are far off enough to stand out as is the "83", which suggests something other than Bowie's left hand. The "s" in "best" and "wishes". Look at just the ink application in the strokes. On the left there is variation is pressure and width, on the right...
The genuine example on the left was signed for a producer. There are a couple of other covers signed for this person dated 1983. These are not very similar. The first 15% of the "B" in "Bowie" reveals a serious problem. There are many observable differences in the inscription and "autograph" on the right. One thing is the placement - it suggests a missing inscription. And once you see where this presentation came from, on the same album, you have a lot to look at. It is a reasonable attempt, but fails in a large number of ways.
Look at the genuine on the left. Look at the fast, deliberate nature of the up-and-down creation, vertically, of the word "with". Then look at the LP on the right.
Finally, look at the trail-off points for the pen. The LP on the left, apart from exhibiting the expected variation in stroke width, also shows nice tapered ends of strokes indicating speed. The LP on the right does not show this - in places like the very end of the "B" for example where we are to believe speed caused him to break the "B"...
Click for a larger image: