Phil Shrimpton has a copy of this for sale in his latest ebay auctions and until I came across it I'd forgotten all about compiling it. I think it was a supplement to issue No 4
of British Comics World which was a special Dudley Watkins edition if memory serves and it contained, in its eight A4 sized pages, a listing of all the Desperate Dan reprint strips that filled the Dandy's pages between Watkins' death in 1969 and 1983 when the reprints were replaced by new strips. This information would have found its way into the Dandy Monster Index if only there had been space for it. I also think the supplement contained a listing of Watkins work for annuals which didn't manage to fit into the actual BCW Watkins special.
I'll have to get into the loft and reunite myself with my copy just to see exactly what it did contain when it was published over thirty years ago.