On the left are 2 autographs that look identical at first glance. Thankfully, there are a number of giveaways that help identify the fake one.
1. The real David Bowie autograph was signed in 1973 and by 1974, Bowie had almost completely dropped signing "David". By 1976 he was just "Bo".
2. The forgery (currently on sale on a memorabilia website) is signed on the LP cover of "Lodger"...released in er...1979.
1. The M is not typical - its too long.
2. The h is too rounded and letters close together.
3. Bowie rarely looped a k in this manner - I have seen it only once on a 1972 autograph signed at The Roundhouse.
4. Bowie's left hand made his v's and w's distinctive which this person failed to replicate
5. An extra squiggle added between the i and the d - the d is untypical
6. The B (Bowie's biggest distinguishing mark) is not typical and this has clearly written by a right handed person.
7. Non typical w with a semi-low link to the i
To the left is a study by a trusted Bowie collector and authenticator, Eric K Longo. The "Rapture" original on the left was one of a number of LP's DB signed for Mike, a BBC radio employee in 1983, that came onto the market recently.
Again at first glance they look VERY similar until you break down the giveaways - in this instance the untypical letters, again done by a right handed person , the signature and the numerals.
If in doubt please check first with an authenticator.