M2 ammunition boxes repurposed for OBSRBOMBE M/66 - but what are they ?

[Linkman]

Here are two US M2 ammunition boxes (ARTCRAFT and UNITED) that I recently acquired. The original (yellow) stencilling has been overpainted OG and the boxes repurposed / refilled, as shown by the (white) stencilling.
I think HMAK and crown = Hærens Materielkommando (Army Materiel Command), Denmark, which was disbanded 2007 - internet source.
The LOT and PK numbers indicate 1988 & 1995 filling, each with 50 pieces of OBSRBOMBE 'pyrotechnic articles' M/66.

I've tried to search for a precise description of these pyrotechnics on the assumption they are illuminating flares and small enough that 50 will fit in the boxes, but have been unsuccessful. I would appreciate assistance in identifying these items.

Also, there are blue flashes on two diametrically opposite corners of the boxes - what do these signify ?

 

[Defender]

The OBServationsRøgBombe M/66 (Observation Smoke Bomb M/66) is a pyrotechnic signaling device used by the Danish Armed Forces for combat simulation and hit indication during military exercises. Primarily used to generate a visible smoke cloud with a low acoustic signature. It has a short fuse for ignition.

The blue corners on the boxes just indicate training ammo/pyrotechnics.

Picture from the www:

 

[Linkman]

Many thanks for your detailed reply - answers my questions completely.