I am frequently shown copies of apparently genuine autograph letters signed by Churchill and written entirely in his own hand. To the disappointment of many, they are not originals, but extremely good facsimile copies from Churchill’s Private Office.
At least nine variations of replica printed holograph notes were reproduced by the thousands by to thank well-wishers, whose congratulations poured in on important dates such as Churchill’s birthday. They are very nicely produced and appear original; some appear actually to be color separations, since they are in blue-black ink and are not just black-and-white. But they are not originals and were not signed by Churchill personally. Every so often, the Private Office would have him write one out, and then reproduce it for their use. (The original was then destroyed.)
The key is that these facsimiles lack a salutation. Secretaries would simply place them in envelopes and mail them by the hundreds to anyone who sent him a greeting. Occasionally they would type the name of the recipient on the bottom of the note, but the volume was too great to allow much of this. The value of these facsimiles on the market is incidental. A true autograph letter by Churchill is, of course, worth much more.
The definitive article is “Those Realistic Holograph Letters” by James Mack, Finest Hour #115, Summer 2002, available from The Churchill Centre or as a .pdf download from their website.