On May 17, 1983, while serving time for a prior conviction, prison officials conducted a routine inspection of defendant Chris Prestenbach’s personal property. They discovered that a lotion bottle in his possession contained a plastic bag with six Postal Service money orders inside. Four of the money orders had been altered.
Prestenbach was indicted and convicted of four counts of violating 18 U.S.C. § 494.1 Each count had charged him with knowing possession with intent to utter and publish as true one of the altered money orders. The district judge sentenced him to five years for each violation, sentences to run consecutively. Presten-bach’s direct appeal challenged the sufficiency of the evidence and an evidentiary ruling. This court affirmed the conviction without opinion in 1986.
He was released from state custody in 1993, and after the completion of his first sentence, he filed a motion under Federal Rule of Criminal Procedure 35(a)2 to correct his sentence. He argued that his sentence punished him four times for a single offense. Since his first five-year *782term had been completed, he argued he should be released. The district court denied his motion.
Prestenbach appeals.
I
As a threshold matter, Prestenbach argues that the sentencing court lacked subject matter jurisdiction and therefore his conviction and sentence are invalid.3 He argues that 18 U.S.C. § 494 does not prohibit possession of altered postal money orders, and thus his indictment failed to state a claim.
We cannot revisit his conviction. Under Rule 35(a), a defendant cannot challenge his conviction; he can only challenge his sentence.4 Further, this court cannot construe his Rule 35(a) appeal as a 28 U.S.C. § 2255 motion5 because the one-year statute of limitations on filing a federal habeas petition expired years ago.6
Focusing then on the court’s jurisdiction to sentence, we rule that subject matter jurisdiction did exist. Defendant’s indictment alleged violations of 18 U.S.C. § 494, clearly a federal question. The indictment alleges every element of the crime. That Prestenbach’s alleged acts do not violate section 494 goes to the merits of the case, not jurisdiction. This alleged error should be addressed as a failure to state a claim, not as a jurisdictional defect.7 We now address the merits of Prestenbach’s claim.8
II
Prestenbach contends that he is guilty of only a single act of possessing four altered money orders, and thus his consecutive sentences punish him four times for a single crime. We must determine the “unit of prosecution” Congress created — the act of possessing money orders, or the act of possessing a single money order.9 As there is no precedent directly on point, we interpret the text with the aid of analogous cases.
The statutory language is ambiguous. It prohibits possession of “any such ... writing.” Although the government ar*783gues that “any” indicates each writing comprises the unit of prosecution,10 courts have not so held. In Bell v. United States11 the Supreme Court interpreted the Mann Act, which prohibited “knowingly transport[ing] in interstate or foreign commerce ... any woman or girl for the purpose of prostitution or debauchery, or for any other immoral purpose,”12 to allow only one conviction for the simultaneous transportation of two women. The Court noted that, lacking explicit instructions from Congress, it would treat each transportation as the unit of prosecution.13
Since “any” can mean “one” or “some,” 14 courts have determined the unit of prosecution by reference to the conduct alleged. Courts apply the following rule: “Whether a transaction results in the commission of one or more offenses is determined by whether separate and distinct acts made punishable by law have been committed.”15 The principle underlying this rule is that the “unit of prosecution” for a crime is the actus reus, the physical conduct of the defendant.
While identifying the actus reus with particularity may not always be easy, our cases have been able to do so in a coherent fashion. If the statute prohibits uttering false statements or stealing mail, courts treat each utterance or theft as a single offense. Thus, fraudulently endorsing eight checks at one time constitutes eight violations of 18 U.S.C § 495.16 Submitting two documents with false statements at the same time supports two convictions.17 However, stealing a single bag of mail with sixteen pieces of mail in it is only a single offense.18
Cases interpreting statutes criminalizing possession of firearms or stolen mail follow the same logic. If the contraband is possessed at a single place and time, there is a single act of possession and a single crime.19 Possession of multiple pieces of *784stolen mail that were stolen at the same time gives rise to only a single offense.20 The “simultaneous, undifferentiated possession of multiple firearms constitutes only one offense” under statutes forbidding convicted felons from possessing or receiving firearms.21 Consistent with the principle that the actus réus defines the unit of prosecution, the cases involving firearms acknowledge that receipt or possession of different guns at different times could give rise to separate offenses, with consecutive sentences.22
Turning to the facts of this case, we find that the government alleged only a single act of possession. As noted above, whether a transaction results in the commission of one or more offenses is determined by whether separate and distinct acts made punishable by law have been committed. Keeping four altered money orders in a lotion bottle is one action, and therefore one crime.23
If the government proved separate acts leading to his possession of the altered money orders, it might present this court with a different case;24 but it did not. Nor did the government allege any acts of alteration by the defendant. Therefore, we REVERSE the district court’s denial of defendant’s motion to correct his sentence and INSTRUCT the district court to reduce the three illegal sentences and grant any additional appropriate relief, including Prestenbach’s release.
Sentence VACATED and REMANDED.