Hi Jigjag, he is one of many who have turned me prematurely grey over the years. Yes, it is a sort of drum. Sorry, I have recycled the clues and cannot remember what it was so cannot help with the parsing.
Jigjag, bill = TAB, inside rock = AA, and number = L (50).
And dja, I'm sure you're right but I bet I'm not the only one who put numbers in as he went along just to keep track of things. I could redo it but I won't bother! Thanks.