Online catalogue that explains differences between pick#

Anybody knows a good resource to find the differences between pick numbers. Sometimes differences are quite obvious, but sometimes they are so subtle that I can't manage to figure them out. Colnect sometimes describes the differences, but mostly not ...

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Verweis : "BramVB"​---------------
​We need notista !!!
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I find the Bank Note Museum http://www.banknote.ws/ to be very helpful. Not only do they mention details specific to the note shown, but they also have links to similar notes.

Verweis : "BramVB"​​---------------
​We need notista !!!
​---------------

​hear hear!