Finnegan's Wake

Detective Finnegan tells Falsone "I've been waiting for this moment since I first got a callbox key" and Falsone replies "what's a call box key?". A callbox, also known as a police box, was a type of public telephone kiosk for use by the police, and by the public in emergencies. Callboxes were most widely used in the United Kingdom from the late 19th century through the mid 20th century, they became part of pop culture because of the series Doctor Who (1963) whose TARDIS time machine was disguised as a police callbox. However callboxes actually originated in the United States, the Chicago Police was the first department in the world to install a callbox in 1880, Washington D.C. installed its first in 1883, Detroit in 1884, Baltimore and Boston in 1885 and New York City in 1889. Callboxes severed as both mini police stations for officers to use to fill out reports and take statements, they also contained supplies like first aid kits, fire extinguishers and larger ones held shotguns, rifles and extra ammunition for emergencies; so for obvious reasons they were kept locked and each officer was given a callbox key. Their most important feature however was a telephone with a direct line to the nearest precinct, while the inside of the callbox was only used by police they were configured so the public could access the phone, some had a phone inside the box that could be accessed through a small hinged door, others had a phone on the outside of the box behind a glass shield that could be broken in emergencies by the public. After the advent of the 911 system in 1968 callboxes became less needed but continued to be used, at this point the phones were connected to the 911 system instead of directly to the police. The Baltimore City Police Department used callboxes for 100 years, they were a kiosk style box with a small interior for officers to make reports and get extra supplies if needed, the last version used had a payphone style box mounted on the outside that automatically connected to a 911 operator when the receiver was picked up; Baltimore's first callbox was installed in October of 1885 and the last one was removed from service in December of 1988.

Detective Finnegan mentions the bullet that killed Clara Sone was a .32 rimfire. However with just the bullet and no shell casing there would be no way to determine this.

The .32 rimfire was one of the first metallic cartridges made, it was developed in 1860 by Smith & Wesson, there were also a few different rimfire cartridges made by Colt, Henry and Remington, but by the 1890's there were several .32 caliber centerfire cartridges as well, the bullets used by the rimfire and centerfire versions are the same, there's no way to tell if a bullet was fired from a rimfire or centerfire cartridge without the casing. Plus it isn't too likely it was a .32 rimfire, by 1930 it was fairly uncommon as the centerfire version had much better performance, production of .32 rimfire guns had all but ended by the 1920's; although ammunition for them continued being made until 1941.