(concurring, with whom Cordy, J., joins). I concur with the result reached by the court, as it is an unavoidable one *179on the record and argument presented to us, but write separately to echo the sentiments expressed in the concurring opinion of the Appeals Court. Commonwealth v. Barros, 49 Mass. App. Ct. 613, 620-621 (2000) (Jacobs, J., concurring).
It appears likely that the circumstances known to Officer Mc-Dermott did include an objective basis for suspecting that the defendant did not have a license to carry a firearm (i.e., the defendant’s apparent youth), but the Commonwealth failed to introduce sufficient evidence on that decisive issue. As the Appeals Court noted, evidence that the defendant appeared to be underage, had it been presented, would have justified a reasonable suspicion that the defendant did not have a license to carry a firearm. At the time of this stop, G. L. c. 140, § 131, as amended through St. 1996, c. 200, § 28, provided that a license to carry firearms could not be issued to anyone under eighteen years of age.1 The defendant was seventeen years old. (one month shy of his eighteenth birthday) on the day he was stopped. Officer McDermott testified that he knew the defendant as one of “a group of kids that live in that area,” but provided no assessment (beyond characterizing him as a “kid[]”) as to whether his appearance was sufficiently youthful to make his eligibility for a license to carry firearms appear unlikely. The presentation of that additional piece of evidence would have taken only a single question of Officer McDermott.2 However, the officer’s mere reference to the defendant as a “kid[j” and the motion judge’s reference to him as a “young man” do not allow us to draw the more precise conclusion that he appeared to be less than eighteen years old.
On appeal, the Commonwealth’s brief referenced another potential ground (G. L. c. 140, § 129C) that would arguably justify this stop, but did so only in a single, conclusory sentence *180that does not rise to the level of adequate appellate argument. Hence, the court’s opinion justifiably refuses to consider the issue. Ante at 178 n.10. Mass. R. A. R 16 (a) (4), as amended, 367 Mass. 921 (1975).
The statute provides in part: “Any person who, while not being within the limits of his own property or residence . . . shall on demand of a police officer or other law enforcement officer, exhibit his license to carry firearms .... Upon failure to do so such person may be required to surrender to such officer said firearm, rifle or shotgun which shall be taken into custody as under [G. L. c. 140, § 129D], except that such firearm, rifle or shotgun shall be returned forthwith upon presentation within thirty days of said license to carry firearms . . . .” G. L. c. 140, § 129C. The statute thus gives an officer the right to demand production of a proper license from anyone carrying a firearm and, if such license is not produced, to at least confiscate that firearm until such time as a valid license is produced.3 We have never addressed the power of an officer to stop someone in order to make a demand for a license under G. L. c. 140, § 129C, and the Commonwealth’s failure to brief any of the issues surrounding the proper exercise of such a power prevents us from addressing those issues in this case.4 It is, however, an *181intriguing suggestion, and one that would at least arguably justify a stop on the facts of this case.5
*182In my view, this stop was, either by reference to G. L. c. 140, § 129C, or by reference to the defendant’s apparent age, probably justifiable. Unfortunately, the Commonwealth’s less than “careful and thorough prosecution,” Commonwealth v. Barros, supra at 620 (Jacobs, J., concurring), both at the evidentiary hearing and in its brief to this court, prevents us from affirming the motion judge’s denial of the defendant’s motion to suppress. The purpose of the exclusionary rule is to deter police misconduct. United States v. Calandra, 414 U.S. 338, 347 (1974). Commonwealth v. Sheppard, 387 Mass. 488, 502 (1982), rev’d on other grounds, 468 U.S. 981 (1984), S.C., 394 Mass. 381 (1985). Here, it appears unlikely that there was any police misconduct at all, and the invocation of the exclusionary rule is mandated instead by the Commonwealth’s failure to present the entirety of the factual and legal justification for the officer’s actions. As a result, our reversal now terminates a meritorious prosecution of an underage youth who was carrying a loaded handgun concealed on his person as he and his young friends proceeded along the streets of Brockton. “[Tjhere are few more dangerous street scenarios than that of an adolescent with a gun.” Commonwealth v. Barros, supra at 621 (Jacobs, J., concurring). I thus join in the result reached by the court, but note that it is a regrettable result that was probably avoidable.
The statute was subsequently rewritten and now permits issuance of a license to carry only to persons age twenty-one years or older. St. 1998, c. 180, § 41 (effective October 21, 1998).
Other evidence as to the defendant’s apparent age on the day in question must also have been readily available. Beyond Officer McDermott’s observations, there was presumably a booking photograph taken that same day. Or, merely asking the motion judge to make observations of the defendant in the court room and include them in his findings would likely have sufficed. (The evidentiary hearing was held just two months after this stop, and the judge, having seen the defendant, referred to him in his findings as a “young man.”)
The final sentence of the section leaves open the possibility of prosecution for any other firearms offenses: “Nothing in this section shall prevent any person from being prosecuted for any violation of this chapter.” G. L. c. 140, § 129C.
Officer McDermott’s failure to reference G. L. c. 140, § 129C, in his testimony would not preclude us from considering the issue. It is true that the officer’s testimony covered only what he actually said to the defendant — i.e., “I want to speak with you” and “I wanna talk to you” — and did not expressly state what the intended subject matter of that “talk” was to have been. Because the encounter took a sudden turn when the defendant reached for his waistband, the record could not reflect the contents of the conversation that would have taken place had the defendant stopped and spoken with the officer. It is safe to infer, however, that because the only purpose in speaking to the defendant concerned his carrying of a weapon, that intended “talk” had something to do with whether his possession of a gun was lawful. (After the gun was taken from the defendant, the officer did ask him if he had a license.)
Moreover, as we have long held, it is not the precise thought process going through an officer’s head that controls the constitutionality of any seizure. Rather, it is whether the surrounding facts and circumstances known to the officer would, viewed objectively, justify the requisite reasonable suspicion or *181probable cause. See Commonwealth v. Santana, 420 Mass. 205, 208 (1995), quoting Commonwealth v. Ceria, 13 Mass. App. Ct. 230, 235 (1982) (“police conduct is to be judged ‘under a standard of objective reasonableness without regard to the underlying intent or motivation of the officers involved’ ”); Commonwealth v. Petrillo, 399 Mass. 487, 491 (1987), quoting United States v. McCambridge, 551 F.2d 865, 870 (1st Cir. 1977) (“validity of an arrest is normally gauged by an objective standard rather than by inquiry into the officer’s presumed motives”). Thus, we need not concern ourselves with whether Officer McDermott actually intended to start his “talk” with the defendant by demanding production of a license. Whatever Officer McDermott’s precise intent or plan was, we need only consider whether the facts and circumstances known to him were sufficient to justify a stop of the defendant pursuant to G. L. c. 140, § 129C.
I do not agree with the court’s assessment that the “anonymous informant” in this case lacked sufficient reliability, ante at 176-177, and I thus conclude that there was reasonable suspicion that the defendant was carrying a firearm.
The facts surrounding Officer McDermott’s encounter with the informant take this case well out of the category of the usual “anonymous tip.” While on patrol in a marked cruiser, Officer McDermott was flagged down by a man driving a white Dodge pickup truck. Officer'McDermott described the man as a “[m]iddle-aged white male, salt and pepper type hair, short, stocky.” The man was “well-dressed,” wearing slacks and “maybe a collared shirt.” He identified himself as “a local businessman” who worked on Main Street. The man appeared “concerned.” The man “asked to remain anonymous,” and is thus properly referred to as an “anonymous informant,” but he is hardly the equivalent of an anonymous telephone tipster who can never be located or identified.
The reliability of persons who contact the police face to face is greater than those who contact the police through completely anonymous and untraceable methods. “An instance where a tip might be considered anonymous but nevertheless sufficiently reliable to justify a proportionate police response may be when an unnamed person driving a car the police officer later describes stops for a moment and, face to face, informs the police that criminal activity is occurring.” Florida v. J.L., 529 U.S. 266, 276 (2000) (Kennedy, J., concurring). See United States v. Sierra-Hemandez, 581 F.2d 760, 763 (9th Cir.), cert, denied, 493 U.S. 936 (1978) (distinguishing unnamed informant who speaks to officer in person from unnamed informant making anonymous telephone call); Giles v. Commonwealth, 32 Va. App. 519, 524 (2000) (reports from two unnamed persons who approached police officer “were not an anonymous tip,” noting that officers can assess credibility of informants who meet with them in person). Here, not only was the encounter face to face, but the man told the officer what he did and where he worked. He appeared both respectable and “concerned.” Given the imminent dangers posed by unlawful firearms on the street (especially ones in the hands of “kids”), the information provided by this concerned citizen was sufficiently reliable to justify police action, notwithstanding the fact that he did not wish the defendant and his *182compatriots to know that he was the one who had alerted the police to their possession of a gun. If reasonable suspicion that a person is carrying a firearm is a sufficient basis for the limited seizure contemplated by G. L. c. 140, § 129C, that threshold was satisfied here.