I have added 30 more Pennies and updated the photos. Thanks to Jorg  for supplying me with these.

Link added to ukpennies

I have now uploaded the images of the Pennies I collected when visiting Ireland.

You can find them here:  Irish Pressed Pennies

How they are made

An early and common method of coin elongation was by leaving them on a railway track. When a train rolls over a penny, the force is sufficient to cause deformation that flattens and stretches it into an oval, showing only the faintest trace of the original design. Some early railway flattened pennies were then hand engraved with the date and location.

Modern elongated coins are created by inserting a standard, small denomination coin into a small rolling mill consisting of two steel rollers pressed against each other with sufficient force to deform the coin. One of the rollers (called the “die”) is engraved with a design that imprints a new image into the metal as the coin passes through it. The resulting coin is oval-shaped and shows a design corresponding to the design on the die in the mill. Some machines are hand operated, whereas others are fully automatic.

Legality

In the UK, the Coinage Offences Act 1936 prohibited the defacement of any current coins. This was repealed in its entirety by the Forgery and Counterfeiting Act 1981, thus removing the prohibition on coin defacement.