This is a companion article to one about Gretsch round badge drums published in December 2020.[i] This study involves Ludwig Keystone badge drums with serial numbers produced from late 1963 to late 1969. Many collectors place a premium on born together drum sets. However, very few vintage drum sets come with original receipts or reliable histories which can assure owners or potential buyers that the sets were originally purchased as one unit from the factory or music instrument retailer. When documentation is not present, many look for sets with closely grouped serial numbers. But how close is close enough?