Can you give us a general idea of what you have? Date range, photos of a couple of the best ones maybe? Someone might be able to give you better advice that way.
It does look like there should be something at the top - perhaps a storage drawer as you suggest. It looks like a nice cabinet though - would it be worth taking it anyway and having something made to fill the gap? You could then customise it to suit.
To be honest, if this was something I wanted I'd be happy with a replica. After all, the original is just a round shiny thing contrived for no other reason than to make money. Leave a nice hole in the album and people will be desperate to fill it.
Referring to Richard's site, he says that it's "distinguishable by there being only 5 border teeth from the upright of the R to the top of the I in VICTORIA".
How was example 6 identified please? https://rarestpennies.wordpress.com/1881h-f103/