For the 1894 half penny there are two die varieties consisting of two obverse dies paired with two reverse dies.  Differences are easily located by checking for the alignment of the letters I and T in BRITANNIAR.  For the reverse dies there is a difference in the spacing in the date.

Half Penny

The spacing is measured between the nine and the four.

Obverse Dies:  BRITANNIAR

Repunched 'R';
Low 'I'

High 'I'

Reverse Dies:  The Date

Large Spacing

Small Spacing