Newbie Needs Stamp Help

Hi All
my wife and I just found in a old box a documentary 5 dollar United States Internal Revenue stamp, in small black letter it says "series 1950" it is in very good shape but was used at one point it looks like.

it looks like some one hand wrote 11/7/1950 and above that 3 letters that I cant make out.

I dont know if this is worth 2 cents or nothing. any general advice would be great. I have tried googling it and nothing really comes up.

thanks all

Welcome,
Sounds like a Scott #R552. Value for a used stamp like your is <$1.00.
Don

The pen marking is a cancellation. There are also handstamp cancels on these as well.

Further, there are cut (slice) and punch (punched hole) cancels which can exist separately or in combination with the others. Those would reduce the value of this stamp to the minimum.

Assuming you are in the United States and have a public library nearby, you might go look to see if they have a Scott Catalog. Look up your stamps in the catalog and you can see if there is any value.
Assuming there is some value, you should know that stamps sell for 25% to maybe 50% of the catalog value, so don't get all excited if they appear to be valuable.
If you plan to sell them, the easiest way is to list them on ebay or find a stamp dealer. You will need to scan them front and back (or photograph) if you list on ebay.

Good luck.