HAMP-A9E6F1: Post-medieval compass dial

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Unique ID: HAMP-A9E6F1

Object type certainty: Certain
Workflow status: Awaiting validation Find awaiting validation

A slightly bent and damaged copper-alloy compass dial of late medieval date (c. 15th century). The disc has notched protrusions at the cardinal points. There is a small central perforation for a (now missing) needle. The upper surface is marked out with very finely incised lines. Lines connect opposite cardinal points and divide the field into quadrants. There is a double circle border within the circumference. There is also a double circle at the centre (max. dia.: c. 14.5mm). In the centre, within the border, is an 'elaborate' quatrefoil picked out with fine punches, with triangles emerging from the angles of the four leaves. Between the two double circles mentioned, at the cardinal points, are the letters 'S', 'O', 'm', and 'O', again picked out with fine punching. These initials represent the first letters of the points of the compass in Latin: Septentrio (north), Oriens (east), Meridies (south), Occidens (west). A parallel can be found illustrated in Margeson (1993, 71-72; ref. 447); although this was found in an 18th-century context the author argues for an early 16th-century date on the basis of the lettering style. Dr John Davis who has been studying this and related pieces suggests a late medieval date in the 15th century. This artefact has developed a mid/dark-green patina with some fine pitting. It has been slightly bent in profile, and has suffered a small bend and crack at the circumference.


As noted below by John Davis of the British Sundial Society this is likely to be the base of a composite object incorporating a sundial. Thanks are extended to him for these useful comments.

Dr Davis has had the compass base analysed to establish its metallurgical composition by B Gilmour in Oxford. It was shown to comprise 89.4% copper, 7.6% silver, with remaining 3.0% small parts tin, lead, iron and other elements. Compared to other medieval devices is has the highest copper content; the high levels of silver suggesting a silver-rich ore. Thanks are extended to the finder for passing this information on.

Find of note status

This has been noted as an interesting find by the recorder.

Class: dial
Inscription: S O m O

Subsequent actions

Subsequent action after recording: Returned to finder


Broad period: MEDIEVAL
Subperiod from: Late
Period from: MEDIEVAL
Date from: Circa AD 1430
Date to: Circa AD 1500

Dimensions and weight

Quantity: 1
Length: 34.15 mm
Width: 33.3 mm
Thickness: 0.55 mm
Weight: 3.28 g

Discovery dates

Date(s) of discovery: Thursday 1st January 2009

Personal details

Found by: This information is restricted for your login.
Recorded by: Mr Robert Webley
Identified by: Mr Robert Webley
Secondary identifier: Dr John Davis

Other reference numbers

Other reference: E2717; 11

Materials and construction

Primary material: Copper alloy
Completeness: Uncertain

Spatial metadata

Region: South West (European Region)
County or Unitary authority: Dorset (County)
District: North Dorset (District)
Parish or ward: Gillingham (Civil Parish)

Spatial coordinates

4 Figure: ST7927
Four figure Latitude: 51.041966
Four figure longitude: -2.300912
1:25K map: ST7927
1:10K map: ST72NE
Grid reference source: GPS (from the finder)
Unmasked grid reference accurate to a 1 metre square.

Discovery metadata

Method of discovery: Metal detector
General landuse: Cultivated land

References cited

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Timeline of associated dates

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1 comment

  • John Davis wrote @ 09:42:51 on the 30th August 2011.

    I believe that this is the base of the compass-box of a late-medieval compendium, (1450-1500) the lid of which would have been a nocturnal (4 examples on the PAS database) and including an equinoctial sundial. There are examples of the complete instrument in the British Museum and the Oxford Museum of the History of Science.

Audit data

Recording Institution: HAMP
Created: 9 years ago
Updated: 7 years ago

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