They both do appear to be written by the same author. But ironically, I remember his signature as being uncannily similar to John Lennon's, aside from the "J" and the "L", no real individual, distinct traditional lettering, sort of just a series of up and down waves. Also, a look at google exemplars reminded me that on the few sigs of his I've seen, they end with the "d" going up, not closed by a return, down-stroke, which is a big difference in letter formation. Of course, he lived a long life, the longer you live, the more subject to subtle and sometimes drastic change. I'd have to have a dating range on his styles of signature to venture a better guess than 45% yes / 55% no to both.
I've got no clue as to when each of these were signed. I can tell you i bought the black inked auto last week and the silver inked auto about 12 months ago - both from different sellers from different parts of the UK.
The black signing was the one i believed to be fake as i only paid £2.20 - too good to be true, right? But, having said that, they both look very similar.
Thanks for the interesting points and observations, Woody. Your comments are very helpful and most welcome.