From the Picattinny Dictionary completed in 1958.  The box held what is known as Zündladung or "Booster Charges."  According to the dictionary "The purpose of this detonator was to pick up the shock wave due to the explosion of the fuze detonator to amplify the effect of the shock wave and in turn to detonate the main booster charge."  I'm assuming these were used with HE bombs dropped from aircraft.  Your box held 40 such boosters.

"Zdlg A consisted of an Al cylinder 2.95" long, 83" in diameter, closed at one end and filled with a pressed RDX/wax-92/8% pellet, density 1.61 and weighing 577 grains. The pellet was tinted blue by the addition of a small quantity of dye.  A cavity was formed at the forward end to receive the detonator which contained 6.5 grains of RDX under 6.3 grains of LA/L st-58.8/41.2% in an enclosed Al tube.  A disc of Al with a central hole held the detonator tube firmly in its cavity.  The ensemble, held by a leather washer and an Al ring, completed the closure by being folded over the lip of the body." (Credit; Neil Hever USA for providing the info)