Bill,
I have several BSP limited editions where the author has inscribed a special signed message to me on the title page, but also signed the colophon page. BSP authors would under certain circumstances sign on both the colphon and the title page, but in the case of the Fante ROAD TO LOS ANGELES the tipped in signed sheets for the lettered edition were made/created years in advance. This is also true of other Fante limited editions as well as other authors from the selected limited edition BSP backlist titles.
Time should always be taken to insure authenticity before making a commitment and regretting if afterward. I know this sounds preachy, but there is no substitute for good old fashioned homework. There are many knowledgeable people in these forums always ready to help others, Take advantage of that wealth of knowledge.
Caveat emptor!