Here is the Kirby sig that I got from the King at the NY Comic Con in 1975. It does appear to flow a bit more than the sig on the FF2, but looks very similar (especially the "K"), and may have a different look owing to being on the splash page rather than the cover:
Thanks - this is similar to what I found through a web search. Although, It's not what's "similar" about a signature that counts in forensic analysis, it's what's "dissimilar". Again we see lower case -script, not block lettering.
I had an Amazing Adventures #1 (1961) that was autographed by Jack and it looked just like the onein the Cap #100....the FF #2 did not strike me as real as soon as i saw it....just my 2 cents....