All bills printed since the early 20th century have seals. They're the circles that appear on one or both sides of the bill's portrait.
US Notes, gold certificates, and silver certificates have the Treasury seal showing a key and a balance scale. The colors were red, gold, and blue respectively. Federal Reserve Notes have two seals - the Treasury seal in green and the Federal Reserve seal in black.
The green seal indicates that your bill is a Federal Reserve Note. Please see the question "What is the value of a 1950 C US 10 dollar federal reserve note?" for more information.
A red seal indicates that a bill is a U.S. Note. The last $10 U.S. Notes were printed in 1923. All 1950 $10 bills were Federal Reserve Notes with green seals.
Please check your bill again, including the banner across the top. A blue seal would indicate that it's a silver certificate, but no $10 silver certificates were dated 1950.
$10
None of them. 1950-series $10 bills remain common among collectors. There's more information at the question "What is the value of a 1950 US 10 dollar bill?".
Click on the link in "RELATED LINKS" and you should see a 1950 $10 bill.
It's the Treasury Department seal and is a mark of authenticity because it indicates the bill is issued by the US Treasury.
None of them. 1950-series $10 bills remain common among collectors. There's more information at the question "What is the value of a 1950 US 10 dollar bill?".
It will have the date "1950" at roughly the 5:00 position of Hamilton's portrait.
Please check your bill again and post a new question. It's either not a silver certificate or not from 1950. All 1950-series $10 bills were issued as Federal Reserve Notes. These have the familiar green seal indicating they're FRN's and have the specific wording Federal Reserve Note across the top of the front of the bill.
99% of the time a 1950 $10 bill is just worth $10. If it is an error, star note, or in perfect condition it could be worth more.
About 10 to 15 dollars in excellect condition