Antiquarians have been intrigued by the ancient Pictish stones for centuries. Some attributed all prehistoric Scottish archaeology to the Picts and developed fanciful notions of them as primitive heathens. Modern historical study of the Picts can be said to have begun with a survey of the stones published by Allen and Anderson as The Early Christian Monuments of Scotland in 1903. Despite many more recent discoveries, their catalogue remains a valuable source for anyone interested in Pictish sculpture, although their three-way system of classification is dated and does not reflect current understanding, particularly of relief-carved monuments. The Drosten Stone, a fine 9th-century cross-slab at St Vigeans Museum.

The elaborately carved Nigg stone, kept in the church at Nigg, Easter Ross.

	Allen and Anderson’s Class I consists of incised symbols, but not crosses, carved into unshaped stone slabs or boulders. Aberlemno no.1 stone - a Class I Stone.

	Allen and Anderson’s Class II includes stones carved in relief, usually on both faces of dressed stone slabs. One face always includes a Christian cross, the other may have Pictish symbols, biblical scenes or other motifs. St Vigeans no.2 stone - a Class II stone.

Class III was defined by Allen and Anderson as early Christian monuments without Pictish symbols. Nowadays this is not considered a useful category. A surviving fragment may belong to a monument that did include Christian imagery. We also know that the Picts created a very diverse range of monuments that did not include symbols, such as high crosses, recumbent grave-markers and sarcophagi, so the grouping is too simplistic. Meigle no.2 stone - a Class III stone.

J.R. Allen and J. Anderson believed their classification to be chronological. It is now clear that Class I stones continued to be produced long after Class II forms had been introduced. Continued use of their classifications may confuse the debate about accurate dating of the stones, and alternative, more descriptive naming categories now exist.