Short answer. Yes. The Revised Penal Code punishes a public officer who, without proper authority, opens — or permits someone else to open — closed papers, documents or objects entrusted to his custody. Curiosity is no defence, and letting a subordinate do it counts as the officer's own act.
What the law says
who, without proper authority, shall open or shall permit to be opened any closed papers, documents or objects entrusted to his custody
Revised Penal Code, Article 228 — Opening Closed Documents. Read the full provision →
The custody is what creates the duty
The article applies to an officer to whom the sealed item was entrusted. That trust is the source of the obligation: sealed bids, sealed envelopes of examination papers, court records under seal, evidence bags, confidential transmittals — all of them work only because the person holding them will not look inside. An officer who opens such an item without proper authority breaks the very arrangement his office exists to serve. Note that the item need not be a document in the narrow sense. The provision covers papers, documents or objects, so a sealed container or package is within it just as an envelope is.
Permitting it is the same offence
The words or shall permit to be opened close the obvious loophole. An officer who does not personally break the seal but allows a subordinate, a colleague or an outsider to do so is punished as though he had opened it himself. In practice this is where most liability arises: the custodian who hands the sealed folder to someone who has no business with it, or who looks away while it is opened. The offence is complete on the opening. Nothing has to be copied, disclosed or used, and no one need be prejudiced — although revealing what was inside can attract separate liability for disclosure of secrets.
"Without proper authority" is the whole defence
The article does not forbid opening sealed items; it forbids opening them without authority. An officer acting under a court order, under a lawful instruction from a superior with power to give it, or under the procedure his own agency's rules prescribe — a bid opening conducted by the proper committee at the appointed time, for instance — is not within this provision. What matters is that the authority existed before the seal was broken and can be shown afterwards. An officer who opens first and seeks approval later has already committed the act the article punishes. This is also why written instructions, minutes and logbooks matter so much in these cases.
The penalty, and the 2017 peso figure
The penalties are arresto mayor, temporary special disqualification, and a fine not exceeding ₱400,000. The disqualification is often the harder blow, since it bars the officer from the office he held. That ₱400,000 is the current amount, set by Republic Act No. 10951 (2017), which revised the peso values and fines throughout the Revised Penal Code; older reproductions still print the 1930 figure of ₱2,000 for this article. Administrative liability under civil service rules runs separately from the criminal case, and a related provision covers officers charged with the custody of mail. Anyone asked to explain a broken seal should gather the written authority and the custody records before responding, and take counsel.