It was my first time to see such a modular lens...
The inner lenses are mounted in threaded lens holders. All of the lens groups seem to have matching threads, even the back lens, so I could rebuild the lens like this:
() )( )( S ()
or this
() S () )( )(
or this
() S )( )( ()
etc...

I think the seller was genuine, maybe made a mistake while cleaning.
For me here in Australia, cost of shipping makes returning a very expensive option, so I'll be keeping the lens.
If I was in the USA I probably would not.
It seems to cover 8x10 - I'll post a sample this weekend for anyone interested.
Thanks for your comments everyone.