Many years ago I read a gun magazine item about a NIS(now the NCIS) model 66 .357magnum revolver meant for NIS special agents who retire.
The NCIS(name change after the big Tailhook scandal in the 1990s) now uses the SIG P229R .40 DAK.
The US Customs Service(USCS) now the CBP/US Dept of Homeland Security used engraved S&W model 686 revolvers for retired inspectors & agents.
The FLEOA may have more detailed answers;
www.fleoa.org .
CF