How can I identify reissues??

New to classical vinyl. How can I identify speaker corner and Classic recordings from the originals. I'm sure the markings are there but I've missed them on a couple of albums.
the 'under license' language is on all of them. genrally on the back/bottom. etailers generally always list label names.
I have purchased a large collection and am trying to identify some of the rarer ones. The only "licence" language I'm seeing is on Decca's, (Exclusively manufactured for Alto High Fidelity and FMS Fenn Music Service.) Would you know what this indicates?
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.
Rushton, Thanks for the input. Would you know anywhere in this country to buy a copy of The Record Collector's Handbook by Phil Rees? I emailed them in England today but have not heard back yet as to a distributor here. Anyone have a second hand to sell?