Blank checks and documents can be found on e bay by the thousands ...the trick is to link the item to the source for example was John Doe in Milwaukee in 1905? Does the other information add up? Sometimes this takes hours if not days. As far as aging ink it's a simple process and the things that would be obvious on a laser signature are all pretty easy to detect if you know what you are looking for but for obvious reasons don't want to discuss them on a public forum.
Another thing I've noticed since we are talking about checks is many years ago a cache of MORDECAI BROWN checks surfaced these were all from his gas station and he endorsed the verso. Those are unquestionably good but many of the checks were signed FOR him by his wife. Easy to spot. But what some grifters have done is cut the checks signed by the wife which are worthless in half and then endorse (forge) Brown's signature on verso. These are relatively easy to spot as the checks are NOT signed in the place where a check is normally endorsed and instead signed on the opposite end of the check
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ALWAYS BUYING VINTAGE AUTOGRAPHS
jim@stinsonsports.com