The die proof of the 2.5d for the 1898 New Zealand definitive set, engraved by Hill, has the endorsement 'SHELL with Mr. Rapkin', which implies that Joseph Rapkin Jr also worked on this particular die.
Mr Hill's work on the 1940 New Zealand centennial issue involved a lot of reworking of details. After the die proof for the 4d stamp had been submitted, Hill was asked to make a number of changes: the engine had to be made smaller and the bullocks larger, the frame had to be adjusted and a wireless aerial had to be added to the steamer to make it historically accurate.
The engraving of the 1 shilling, too, proved troublesome. Hill found it hard to engrave the large tree in such a way that it would not end up resembling a stone tower. The work involved many trial printings and even when a finished die proof was finally submitted, changes had to be made to the fern alongside the tree. It had to be put back in perspective so as to emphasize the size of the tree.
In 1941, Hill engraved the 25g value from the set issued by the Polish exiled government in London. His design of the moment the Germans demolished the statue of the poet Adam Mickiewicz was based on a photograph taken by a member of the Polish underground that had been smuggled to England via a secret route Die proofs of this value exist in black.
Hill also engraved the top value of the second issue for the polish exiled government, the 1z50. The design shows a scene in an underground newspaper office. The name of the paper being printed is clearly visible as being the Rzeczpospolita Polska (Polish Republic). Originally, the name of the paper read Polska Zyje (Poland is Alive), but this was changed after it was discovered that this newspaper was opposed to the exiled government. Die proofs are thought to exist with this original name before the change was made.
You will find A. B. Hill's database HERE.