Five similar locomotives, classified E10, were introduced in 1901.

Robertson states that locomotives were introduced on the Ballochney line in 1840.

When electric locomotives were introduced, the same scheme was applied to them.

The first ten locomotives were introduced in 1870 to replace 1849 built 4-2-2s.

By the early 1980s, new electric locomotives in the form of Class 1600 were being introduced.

Further renumberings have taken place as new locomotives were introduced.

This practice ceased about 1900 when more powerful locomotives were introduced.

Even as more powerful locomotives were introduced, the trains that they pulled became heavier.

The locomotives were introduced in the Midland region later.

This locomotive was introduced from 1972, after electrification of several industrial lines.