Mionnet's scale

A scale, 19th century, used to describe the size of coins, medallions, and similar flat round objects, published as an illustration by the French numismatist T. E. Mionnet in 1805.

The intervals are irregular and it is not known why Mionnet chose them. Since the scale was defined by a printed image, not numerically, and paper changes size at different humidities, it is not possible to say very precisely what Mionnet originally intended.

A number of authors republished the scale in the nineteenth century, but with varying dimensions.

Earle Caley measured specimens of these illustrations to an accuracy of 0.1 mm, and the figures in the table below are his. He cautions that, for the reasons mentioned above, a description of a coin's size given in Mionnet's scale are no more than 0.5 mm accurate, and probably less. See Caley's book for a full discussion of the scale.

The dimensions in the table below are diameters expressed in millimeters.

Scale
Number
Mionnet,
1805
Leake, 1854 Dickeson,
1859
Prime,
1861
Head,
1887
1 8.9 I 9.3 9.5 7.5 9.3
2 12.1 II 12.1 12.5 14.0 12.3
3 15.4 III 15.3 15.3 20.1 15.3
4 18.1 IV 18.1 18.3 24.2 17.8
5 21.2 V 21.2 21.3 28.2 21.0
6 23.7 VI 23.8 24.2 32.1 23.9
7 26.6 VII 26.6 26.6 40.4 26.1
8 28.9 VIII 28.8 28.9 43.0 28.4
9 31.8 IX 31.4 31.3 45.7 31.2
10 35.2 X 34.9 33.9 48.3 34.7
11 37.7 XI 37.5 36.5 52.3 37.5
12 40.5 XII 39.7 39.0 55.1 39.7
13 43.4     42.1 57.8 43.2
14 51.8     50.4 60.3 51.0
15 56.7     54.9 62.9 55.9
16 60.6     58.7 65.8 60.1
17 64.5     62.8 68.6 63.2
18 70.9     68.8 71.6 69.8
19 78.3     75.9 74.6 77.0
20       83.1 82.1  

T.E. Mionnet.
Description de Medailles Antiques.
Paris, 1805.

Page xiii and plate.

Earle R. Calley
Metrological Tables.
New York: The American Numismatic Society, 1965.
Numismatic Notes and Monographs No. 154.

See the Introduction.

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