The Aerovons found it while they were recording at Abbey Road Studios.
I got this from the old forum, a post by a guy called Alan
Here's an interesting fact! In April 1969, The Aerovons were recording at Abbey Road Studios, and after the session they were shown to a room where they could store their instruments. The room was very small and stacked with drum and guitar cases which obviously belonged to other bands.
One day, curiosity got the better of their drummer Mike, and he decided to have a little rumage around the room. Then Mike taps Tom Hartman (lead singer/guitarist) on the shoulder and says "I think you'd better come and see this!". The band followed the drummer into the room and found themselves standing over a drum-case which had "Ringo Starr" stenciled on the side! They opened it and hidden under a stack of guitar strings, they found the world-famous BEATLES bass-drum head!
They hastily grabbed their cameras and set about taking snaps of themselves with the legendary logo! Upon further investigation of the room, the found John's 12-string Rickenbacker and George's "Revolution" Les Paul!
When they'd finished taking their pics, they put everything back exactly as they'd found it in case they were kicked out of the studios!
The Aerovons find Ringo's drum-head and take a few pictures for posterity!
Getting a bit braver, they arrange the Beatles' drum-head next to theirs!