Great idea Don...I was going to do the same...so I'll just add to yours!
(revenuecollector...that's mean?!)
**
For all new collectors / those who think they've discovered a wildly rare & valuable stamp!
Please consider the following 2 stamps:
(if one of you photo geniuses could make these photos the same size, and put them side-by-side - or tell me how to do that - it would be great!)


They both look very similar, correct? Both are US postage stamps, printed in the late 19th century. Notice both are used - and very clearly - both have distinct cancellations from Philadelphia, PA.
The 2nd (smaller) stamp is a priceless gem. It is only one of 2 copies in existence - and the only one in private hands. The last time it was sold - app. 10 yrs ago - it sold for app. $3 million dollars.
The 1st stamp - belongs to me. It is in my own personal stamp album. You too could own one of these - for likely as little as $5, if you were willing to search online for it. For $10-$15, you could get one immediately.
The first one is Scott #85A. Catalog Value: $3,000,000
Mine is Scott #63. Catalog Value: $50
So: what's the difference??
From the front - what you can see - absolutely nothing. The 2 stamps are identical.
But on the back, they are very different.
The valuable stamp has a very distinct 'grill' - an embossed pattern of broken parts of the stamp - originally intended to prevent re-using of postage stamps. There are a small number of different types of these 'grills' - which take significant expertise to correctly identify - and this particular 'grill' pattern is extremely rare.
My stamp - the 'cheap' one - has no grill pattern on the back.
SO:
Just because you've found a stamp that is old - and you also discover that there exists some version of it that is 'rare' & 'valuable' - understand that the differences between stamps is extremely subtle, and takes expertise to determine. Just because it looks like a valuable stamp does not make it so!