A collection of wooden strata blocks that were used as teaching aids. They would have been used on training courses for mine engineers during the 20th century.
Although coal was originally formed in flat horizontal sheets, the action of millions of years of geological movement has meant that it is rarely found like that underground.
Wooden strata blocks were used to demonstrate to miners how the strata, or layers of rock, were often tilted or bent and sometimes broken. It meant that when the coal seam appeared to suddenly stop or change direction at the coalface, miners could understand where the coal was likely to be found next.