This artillery shell casing is made out of an extremely heavy brass material. The 90mm M19 anti-aircraft shell casing was cut down from its overall larger brass casing and converted into a customize ashtray by a WWII soldier. The embossed stamps on the bottom of the shell are clearly visible as well as inspector and military marking stamps. Because smoking was extremely popular during this time period, trench art ashtrays such as these are documented recorded as some of the most popular trench art pieces made by soldiers and sailors throughout the war. What makes this piece even more special is the early war stamp date of 1943.

The 90 mm gun M1/M2/M3 was an American heavy anti-aircraft and anti-tank gun, playing a role similar to the German 8.8cm Flak 18. It had a 3.5 in (90 mm) diameter bore, and a 15 ft (4.6 m) barrel, giving it a 50 caliber length. It was capable of firing a 3.5 in × 23.6 in (90 mm × 600 mm) shell 62,474 ft (19,042 m) horizontally, or a maximum altitude of 43,500 ft (13,300 m).

Prior to World War II, the primary US anti-aircraft guns were the 3-inch M1918 gun (76.2 mm L/40) and 3-inch anti-aircraft gun M3 (76.2 mm L/50), a widely used caliber for this class of weapon. Similar weapons were in British, Soviet, and other arsenals. There had been several upgrades to the weapon over its history, including the experimental T8 and T9 versions developed in the early 1930s, that were intended to enter service later in the decade.

However the US Army became interested in a much more capable weapon instead, and on June 9, 1938, it issued a development contract calling for two new guns, one of 90 mm, which it felt was the largest possible size that was still capable of being manually loaded at high elevations, and another, using assisted loading, of 120 mm (4.7 in). The new design seemed so much better than developments of the older 3-inch that work on the 3-inch T9 was canceled in 1938, just as it became production-ready. By 1940, the second development of the 90 mm design, the T2, was standardized as the 90–mm M1, while its larger cousin became the 120 mm M1 gun.

A few hundred M1s were completed when several improvements were added to produce the 90–mm M1A1, which entered production in late 1940, and was accepted as the standard on May 22, 1941. The M1A1 included an improved mount and spring-rammer on the breach, with the result that firing rates went up to 20 rounds per minute. Several thousand were available when the US entered the war, and the M1A1 was their standard anti-aircraft gun for the rest of the conflict. Production rates continued to improve, topping out in the low thousands per month.

Like the German 88 and the British QF 3.7 inch AA gun, the M1A1 found itself facing tanks in combat, but unlike the others, it could not be depressed to fire against them. On September 11, 1942, the Army issued specifications for a new mount to allow it to be used in this role, which resulted in the 90–mm M2, introducing yet another new mount that could be depressed to 10 degrees below the horizontal and featured a new electrically-assisted rammer. It became the standard weapon from May 13, 1943.