Alto High Fidelity is a reissue company principally known today for their reissues of the EMI catalog. They did some number of reissues from the Decca catalog before Speakers Corner began with its own cycle of Decca reissues.
As to identifying Speakers Corner reissues of the Decca catalog, it can be difficult because they often don't have any differentiating text on the jacket, the label or the deadwax. Perhaps someone else has found a consistent identifier for the Speakers Corner Decca reissues that I've missed.
