There are few signature exemplars better than official documents of one sort or another especially if notarized. When dealing with obscure actors, sports figures or musicians often you do not have much to go on if no exemplars can be found. You have no idea if the signature is authentic if it is just an album page or index card. I thought perhaps if I shared some places that serious collectors of autographs can go to find true exemplars it might be helpful. One place that a signature is usually required is on marriage licenses issued by various county and city governments. Obviously this would require some leg work but might prove extremely profitable. Has anyone checked to see if there is a marriage license for "Shoeless" Joe Jackson? I have posted the World War I draft registration card that was signed by Jackson on here. I will include just the signature below.
Other examples of records kept by governmental bodies that may contain signatures are wills and naturalization records (if the person was an immigrant and became a citizen). Most documents such as these are considered public record and often they can sent for. There are several genealogy sites that have the actual digitized copies of many documents. The best documents that I have found are World War I and World War II draft registration cards signed by the individual. In World War II there was the regular draft registration of men 18-45 and what was called the "Old man's draft" these were older men born between 1877 and 1897. This time period includes vast numbers of sports and entertainment figures. It is a bit of chore to search, and generally you need to belong to a genealogical site to search these records. These records are of course only for males who were born between 1877 and about 1926 or so. It is also useful even if you know a particular autograph to see an extremely early example to compare changes.
Some states have death certificates available online Pennsylvania for example is available from 1906-1963 on ancestry.com. I tried to check if Burt Mustin might have signed as the informant on his father's death certificate unfortunately he didn't. This is another source to check for exemplars.
One tip is to know the birth name of the individual in order to find that sometimes you need to check the obituary of the individual. Fortunately The New York Times has an archive available online this is an obituary for Delos Jewkes (the voice of God in The Ten Commandments) http://www.nytimes.com/1984/07/19/obituaries/j-delos-jewkes.html
One pitfall of this is that you need to be certain that the person in the draft registration is the exact entertainment or sports figure you are looking for. Often just by checking the occupation of the person can tell you if they are an actor, musician or sports figure. Otherwise birth dates and places of birth can be helpful. Remember that many public libraries have subscriptions to genealogy sites so you may not have to actually purchase a subscription. The originals examples shown are all in the National Archives.
Here are some examples from World War I and World War II draft registrations:
"SHOELESS" JOE JACKSON
JOE CREHAN this is an example of using his legal name Joseph Creaghan rather than stage name. Crehan was in scores of movies mostly in bit parts. He also was on several episodes of The Andy Griffith Show.
CHARLES P. THOMPSON signature on his World War I draft registration card. His occupation was "Advertising" and his birth of 2 Jan 1891 in Philadelphia, PA matches the information on internet movie data base. He was an old character actor best known as Asa the bank guard on The Andy Griffith Show.
DELOS JEWKES is perhaps best known as the "voice of God" in the epic movie The Ten Commandments. This is a World War II "Old Mans Draft" registration.
DICK ELLIOTT another old character actor best known as "Mayor Pike" on The Andy Griffith Show.
Thank you Steve I appreciate that.
I agree that in regards to baseline characteristics a line (including notepaper or checks) may be an inhibiting factor in some signatures. The advent of online resources for governmental documents is most valuable in instances where there are no other exemplars readily available. Of course most official documents are normally not hurried signatures that one might find on an album page, baseball, or checks and receipts. Thanks so much for the comments!