[Rover]

The very old Sigma lenses are a bit of a gray zone... For example, I have the Sigma 14mm f/2.8 EX HSM lens that is not labelled DG - I believe there was never a DG version of that, it was just discontinued - which has worked fine on every Canon camera it's been paired with (40D, 1D Mark II N, 1D Mark III, 1D Mark IV, 1D X, 450D, 650D, 5D Mark II, 5D Mark III etc.) This model is from 1997/8 and has been discontinued in the mid-00s, so Sigma HSM lenses of similar vintage (denoted by the "crinkle" finish, or whatever it's called) are probably fine. Not so sure about the lenses from the "Zen" finish series that preceded it though.