About the Design:

Obverse
The portrait of young Constantine II left, date below

Lettering: 
ΚωΝCΤaΝΤΙΝΟC ΒaCΙλΕΥC ΤωΝ ΕλλΗΝωΝ
·1970·

Translation: 
CONSTANTINE KING OF GREEKS
·1970·

Reverse
Crowned arms (shield with cross) with the defenders of the Crown, denomination below

Lettering: 
ΒaCΙλΕΙΟΝ ΤΗC ΕλλaΔΟC
• 50 λEπTa •

Translation: 
KINGDOM OF GREECE
• 50 LEPTA •

Metal    Copper-nickel
Weight    2.3 g
Diameter    18 mm
Thickness    1.19 mm
Shape    Round