Simulated pilum head.
Note: this is not accurate an historical version but is potentially a suitable teaching aid along with this information. The differences are as follows, The base of the head is too long, it is also not square enough. The metal shaft is too thick in relation to the point and tang, and the tang should be riveted not bolted.

The pilum (plural pila) was a heavy javelin commonly used by the Roman army in ancient times. It was generally about two meters long overall, consisting of an iron shank about 7 mm in diameter and 60 cm long with pyramidal head. The iron shank may be socketed, but more usually widens to a flat tang; this was secured to a wooden shaft. Legionaries of the Late Republic and Early Empire often carried two pila, with one sometimes being lighter than the other. Standard tactics called for a Roman soldier to throw his pilum (both if there was time) at the enemy just before charging to engage with his gladius. They could also be used in hand to hand combat, or as a barrier against mounted charges.
 
See aditional pictures for more details of these pila.

Could also be used as display piece.
 
Weighs: 860g
Overall Length: 670mm (26.5 inches)
Spear Length: 465mm (18.25 inches)