I agree about Scott being the best catalogue for this job.
I'm going to assume that you don't have much familiarity with Scotts, so I apologize if any of this is too basic.
Scott assigns a design number, that might get reused over several actual catalogue numbers. The picture typically isn't reprinted when you see a reused design number. So, a given design number might cover many catalogue numbers.
Scott is pretty good about listing other options at the bottom of a listing...they give you places to look for similar stamps.
I also agree that there is no substitute for reading the introductory materials to the catalogue. Actually, this true for any of the catalogues, and it is worth doing from time to time. I still find new information in the introduction to Gibbons, and I don't know how many times I've read it.
