Dave: a quick Google search provided the history of this battalion in WWII:
http://findarticles.com/p/articles/mi_m ... _n16057444
It helps to know what the unit did in the ETO and who it was attached to, so you can help identify markings and know more about the unit. Here is the first page of four pages on the battalion:
Originally, the 86th was designated to fire chemical shells, but Allied and Axis forces in World War II observed policies against the first use of chemical weapons, so the battalion served in their secondary role--providing conventional indirect fire support to front line infantry troops. The 86th Chemical Mortar Battalion used its 4.2-inch mortars to deliver white phosphorous (WP) shells (for smoke screening and casualty effect) and high-explosive (HE) shells.
In May of 1943, the 86th Chemical Mortar Battalion (Motorized) consisted of cadre from the 1st Separate Chemical Company at Camp Swift, Texas. (1) The basic training program consisted of short, intense, and rigorous missions to prepare the battalion for close support to infantry forces (conditions that the unit would face during combat operations).
Under the command of Lieutenant Colonel Hamilton, the 86th departed Camp Swift, Texas, on 11 April 1944. Traveling by rail and ship, the battalion made stops in Greenock, Scotland; Port Sunlight, England; and Stonehenge, England, before arriving in France on 29 June. Bravo Company ran into trouble en route when their ship either struck a mine or was torpedoed. Company commander, Captain Edward M. Overbeck, and his men immediately went into action to save Soldiers from the sinking ship. The explosion on the ship tore apart loose hatches and dumped Soldiers below deck. This was extremely dangerous because the lower level held many motor vehicles, some loaded with HEs. The ship was rapidly filling with water and oil. Captain Overbeck immediately took control of all other units on deck. Disregarding his own personal safety, he went to the lower level and instructed the safe removal of more than 50 wounded personnel and ensured that every man was safely aboard the landing ship, tank (LST) that came to the rescue. Bravo Company went back to England to reorganize, while the rest of the battalion continued on to France to participate in missions leading up to D-Day. Captain Overbeck and several of his men received Bronze Stars for their actions, bravery, and heroism.
The battalion's first mission was to provide combat support to the 8th Corps
. During this time, the battalion fired more than 11,500 rounds of mortar ammunition for close support of five divisions. Although they were created for combat support, chemical mortar battalions often found themselves in other supporting roles. The experience of Alpha Company on 6 and 7 July of 1944 is a great example. On D+25, Alpha Company docked in the man-made harbor of Beachhead Utah, surrounded by the floating hulks of other ships that never made it to the shore. The company was attached to the 90th Infantry Division in support of the 358th and 359th Regiments.
The 90th began its attack in the early morning of 3 July. All through the day, the mortar crews of Alpha Company persisted in the battle and created an opening for the infantry troops. The 86th fired seven smoke screens while the 90th was forcing a bridgehead across the Seves River. An eyewitness at the scene reported that "machine guns and rifles were blasting all over the place, and you couldn't begin to count the dead...." But the best gauge for measuring the accuracy of the mortar fire was the speed of the advance of the 90th--a half mile in a half hour. Later, many captured Germans wanted to see this "automatic artillery" that was so deadly in its speed and accuracy. Two infantry division commanders later recommended Alpha Company for commendation for its superior battle performance and devotion to duty during the counter-offensive.
The battalion went on to Northern France and contributed immensely to the captures of Saint Malo, Dinard, and Cap Frehal in August of 1944. The battle plan called for the mortar companies to fire WP on the fort at Saint Malo. On 16 August, Charlie Company fired hundreds of WP rounds on the citadel. A communications wire that ran from the fort to the outside was cut with the assistance of the 86th. A day later, the enemy capitulated. In his surrender, the German commander, Colonel Andreas von Aulock, cited the WP barrage as his reason. Two officers and two enlisted men from the battalion were among a group of American officials who accepted the surrender of Colonel von Aulock at the citadel at Saint Malo.
During the period of 24 August to 19 September 1944, the extremely high volume of accurate, close support fire provided by the 86th played a huge part in the fall of Brest and the capture of the Crozon peninsula. It was there that the German prisoners of war nicknamed the WP shell Whispering Death, because it could not be heard in flight. The assault on Brest began on 15 September, and the city surrendered the following day. Personnel from the 2d Infantry Division cited the effectiveness and accuracy of the 4.2-inch mortar in street fighting situations. Personnel from the 86th were able to fire the mortar over tall buildings and provide support to within 100 yards of the front lines.