countersign vs sign

Some examples from the web:

• The operator shall countersign this report and take the necessary corrective measures.
• The ICCAT regional observer shall countersign the prior transfer notification and the ICCAT transfer declaration.
• But I don't know who you are, not without that countersign.
• What is the countersign?
• The Commissioners cannot countersign the declarations of the Directors-General.
• The Joint Managing Authority designated under each joint operational programme may countersign the financing agreement.
• I ask you once again: will you be willing to countersign the report?
• Didn't know the countersign.
• That means either parent can countersign and make a withdrawal.
• No one's done a paper countersign in 20 years, Charlie.
• I note with satisfaction that it was possible to countersign the association agreement with Egypt a few days ago.
• I'd appreciate if you could countersign and get them back to me soon.
• The carrier may require the shipper to countersign the original or a copy.
• I'd appreciate if you could countersign and get them back to me soon.
• The customs authorities shall endorse accordingly the original and the two copies of the attestation of equivalence, and shall countersign the original and the two copies of each extract.
• And once you countersign...
• In implementing those contracts, the OFPPT refused to countersign acknowledgments of receipt for goods, even though it used the products at issue, which were properly supplied by the applicant.
• The operator must countersign this report and take the necessary corrective measures.
• Would you like to countersign retracing Rogers?
• I'd appreciate if you could countersign and get them back to me soon.

Some examples from the web:

• Your heart shows no sign of weakness.
• They are a sign that reconciliation...
• Which makes the L10,000 sign completely pointless.
• And that's our entry sign.
• Fasten seat Belt sign has been illuminated.
• Just like Sagittarius is a fire sign.
• No sign of any nitrates or bomb-making materials yet.
• Short jokes are a sign of desperation.
• But by sign is this one.
• Eye problems could be a sign of inadequate dietary control.
• There's no sign of elijah anywhere.
• Drunken behavior can sometimes be a sign of neurological impairment.
• A plus sign means deficit-reducing measures.
• This is a hopeful sign towards democracy and self-determination.
• Still reeling from that 13th astrological sign.
• Our scouts report no sign of enemies.
• There was no sign of a mechanical malfunction.
• Sweep the theatre for any sign of incursion.
• Finland's acceptance is a sign of subservience.
• Juries see nerves as a sign of guilt.