If you conceal, then you better conceal very well in the First Circuit according to Schubert v. City of Springfield.

Plaintiff-Appellant Greg Schubert brought a civil rights claim pursuant to 42 U.S.C. ยง 1983 against the City of Springfield and police officer J.B. Stern. Schubert 1 alleged that his Fourth and Fourteenth Amendment rights were violated when Officer Stern stopped him in front of the Springfield courthouse to investigate Schubert's possession of a handgun. The district court granted summary judgment in favor of the officer as to all claims against him and dismissed sua sponte Schubert's claims against Officer Stern's employer, the City of Springfield. Having carefully reviewed the facts of the case and the applicable case law, we affirm the district court's decision in full.
The precise location of the gun is inconsequential; what matters is that Stern observed the weapon on Schubert's person. Further, whether or not passers-by saw the gun is immaterial to the question of whether an objective officer who observed Schubert walking in such a manner would possess reasonable suspicion of criminal activity.
. . . once Stern had reasonable suspicion justifying a stop, he was permitted to take actions to ensure his own safety. . . . The officer took several reasonable steps given that Schubert was an unknown armed man walking in that particular location: he emerged quickly from his vehicle, drew his gun, executed a pat-frisk, requested identification and a gun license, attempted to confirm the validity . . . Just as an officer is justified in attempting to confirm the validity of a driver's license, such a routine check is also valid and prudent regarding a gun license.

As it happens, Massachusetts did not have a simple way for police officers to conduct such a check, so Stern's effort to do so took several minutes. But the entire stop took only ten minutes and when Stern realized that he would not be able to confirm the gun license within a reasonable time, he sensibly opted to terminate the stop and release Schubert, but retain the weapon.
And the cop left the man unarmed in a "high crime" area. Nice guy.