Reference: Specialty Dice

In 2nd edition, the boxed game provided three unique types of dice for gameplay.  These were all 16mm D6 dice with custom faces.  If I recall you received two red Sustained Fire Dice, and one each of the white Artillery and Scatter dice.

Sustained Fire Dice

Sustained Fire dice were red D6 dice used to represent the rapid fire ability of numerous weapons in Warhammer 40K.  Oddly (something people frequently got wrong), a unit would roll to shoot prior to rolling Sustained Fire dice.  The dice represented a burst of fire, not spraying bullets/blasts all over the place.  So the burst of fire either struck the target or did not.  If a successful to-hit roll was made, then  you rolled the number of Sustained Fire dice indicated in the weapon's profile.

Common weapons which featured the Sustained Fire dice were Storm Bolters, Shuriken Catapults, and almost every heavy weapon.  In 2nd edition, sustained fire is what separated Plasma weapons from other weapons as well.

The Sustained Fire dice used the following symbols shown above*.  The "Jammed" icon meant that the weapon was unavailable for the next turn (or several turns if you rolled several of these).  This was cumbersome and painful to remember when you were fielding a unit of 10 Eldar guardians, all armed with Shuriken Catapults.

*In the above diagram, the layout has been slightly altered.  On the normal Sustained Fire dice the "ones" and "twos" would be opposite each other.

Certain weapons such as the Assault Cannon could blow up if three "Jammed" icons were rolled in a single attack.

Scatter and Artillery Dice

The two white specialty dice were the Scatter dice (easily recognizable to modern gamers) and the complimentary Artillery dice.  These were used in a number of games at the time and were frequently sold in pairs.  The Artillery dice later disappeared in subsequent versions of 40K.

The Scatter dice were just as they are today, consisting of four sides with directional arrows and two opposing sides featuring "HIT" with a subdued arrow in the 12 o'clock position.  These were used for determining the direction units, weapons, effects, jump packs, etc. moved.  In some instances this die was used alone or in conjunction with 2D6 or a D3.

The Scatter die's sides were laid out as seen above.

The Artillery dice consisted of five sides featuring numbers (escalating by twos = 2,4,6,8,10) and one face featuring "Misfire".  In some European countries and foreign markets the Artillery dice featured measurements in centimeters (CM).  You'll see some with numbers like 20-25, etc.  Those are for foreign markets.  In addition, for non-English markets the Artillery dice frequently came with a burst symbol with an exclamation point inside it --- in place of "Misfire" typed out.

These two dice were frequently used together to determine how a heavy weapon or artillery piece scored its hits.  Misfire + "Hit" often resulted in the weapon catastrophically blowing up over the firing model.  Some weapons such as Ork shootas or blastas actually used the Artillery dice to determine the weapon's strength when firing (i.e. the player would roll to hit and then roll an Artillery dice to determine the weapon's strength; the save modifier being half of the rolled strength).

The use of the Artillery and Scatter dice were frequent and are indicative of the more random and weird-agent rules which were present in 2nd edition.