Philately 101...It is generally wise to assume any apparent rarity, is going to be the common stamp.
Ceylon type A2 (A very handsome stamp)
Scott advice : Type A2 "frequently found with corners repaired"
1859 CV : $6,500 / $1,400
Addressing my example in turn
Perf 12˝, Watermark 1b (Here, I had to eat humble pie, and reach for the Gibbons)

Watermark = 1b (Type SG6)
Damaged and repaired corner. (top right corner)
My $6,500 stamp turns out to be CV$15 (Sc#58A 1867 2s deep blue)

