A number of designs were trialed for the Halfpenny stamp, possibly because it was such an unusual size and no-one was quite sure how it should look or what would work. These are archived at the British Library as oversized images on A4 sheets. The larger ones are approximately 120 x 76 mm and the others 74 x 50mm. They are all based on the final artwork of the building.

None of these found favour and something closer to the final design was trialed with some variations with lower wider proportions necessitating quite radical changes to the building proportions. This seem to have been still a work in progress when the other stamps had been finalised. The Halfpenny may have been the last one to be completed.