It's the Treasury Department seal and is a mark of authenticity because it indicates the bill is issued by the US Treasury.
$10
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.
About 10 to 15 dollars in excellect condition
The green seal indicates your bill is a Federal Reserve Note. Please see the Related Question for more information.
The blue seal indicates your bill is a silver certificate, but "D" is the highest series letter for that date and denomination. In fact, no US bills of any denomination ever reached an "I" series. Please check your bill again and see the question "What is the value of a 1934 US 10 dollar bill with a blue seal?" for information about values.
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.
Despite the 1934 date, yellow-seal bills were actually printed during WWII for use by troops in North Africa. More than one denomination was issued; please see the following questions: "What is the value of a 1934 US 1 dollar bill with a yellow seal?" "What is the value of a 1934 US 5 dollar bill with a yellow seal?" "What is the value of a 1934 US 10 dollar bill with a yellow seal?"
Please check your bill again and post a new, separate question. The last red-seal $10 bills were large-size United States Notes issued in 1923.
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.
He's not on any US coin. He's on the $10 bill.
If it has a green seal, it's worth $12 to $15.
Ten dollar bills are delivered by Federal Reserve Banks in yellow straps 1861: The first $10 bill was issued as a Demand Note with a small portrait of the treasury seal, gray word TEN, and the Federal Reserve Seal were made