My theory is that this is an authentic Yoko Ono signature and someone wanted to make more money by adding a false Lennon to it. Take a $40 signature and make it worth $4000. I do not believe this is authentic.
I also agree the Yoko signature might be good but the John signature lacks the fluidity in the example posted by Ballroom.
This has to be a very close call.
I agree that the example Ballroom posted for comparison looks more fluid but the OP also looks pretty fluid to me. Perhaps just the "nnon" is a little less so.
The fact that the same pen appears to have been used for both autographs makes it seem unlikely that someone has added the Lennon autograph to a genuine Ono.
It would be good to know exactly what the signed item is and when it was supposed to have been signed.