I borrowed some books from Don, one of them being Paul William Schmidt's "History of the Ludwig Drum Company" from 1991 (ISBN 0-931759-49-8). The book is a detailed story of the Ludwig-family, their drum company, their products and all the drummers that have used Ludwig drums over the years.
Of course this is most to the interest of drummers, but for Slade-fans there is also something there. On p. 151-152 the book features a poster that was made for Ludwig's 40 years anniversary in 1984, where they'd invited 75 drummers from all over the world.
Don was among them, as seen on the poster - I've circled him in with red in case you couldn't pick him out. I've also included a close-up where you can see him a little better. Among the other drummers on the poster are Joe Morello, Vincent Dee, Johnny Bee Badanjek, Don Brewer (form. Grand Funk Railroad) Alan White (Yes), Bun E. Carlos (Cheap Trick), Steve Palmer (Steppenwolf), Rick Downey (Blue Oyster Cult) and many more. On the listing of endorsees who were not present "due to schedule conflicts", you'll find names like Danny Gottlieb, Ginger Baker, Nick Mason (Pink Floyd), Eric Carr (Kiss), Roger Taylor (Queen), Darrell Sweet (Nazareth), Joey Kramer (Aerosmith), Bob Benberg (Supertramp) and Nigel Glockler (Saxon). At the table you see Bill Ludwig III and Bill Ludwig II.
The poster-text reads: "Class Act! The most famous drummers in the world…toast the most famous name on drums. On August 26. 1984 these top name drummers arrived in Chicago to celebrate seventy-five years of business. Three quarters of a century of hard work and dedication, something they all know and relate to. That's why they believe in Ludwig, that's why you should too! Visit your local Ludwig dealer soon, and join the celebration."
Bet we wouldn't be offered a glass of champagne, if we did that, but on the poster there seems to be plenty in the hands of those drummers! Anyway, the book also features a special mention of Don on page 161, see below.