Roman Iron Anti-Cavalry Caltrop
3rd-4th century A.D. or later. Composed of four arms tipped with triangular spikes. Cf. Beutler, F. et al., Der Adler Roms. Carnuntum und die Armee der Cäsaren, Bad-Deutsch-Altenburg, 2017, item 204, for type. 24 grams, 73 mm (2 7/8 in.).

Acquired on the German art market around 2000s. From the collection of an EU gentleman living in the UK. Caltrops were scattered on battlefields in an effort to stop or slow advancing enemy cavalry or foot soldiers; regardless of how a caltrop lands, one spike is always facing upwards. Caesar used widely them at Alesia (Caes., BG 7.73? 82): 'Stakes a foot long, with iron hooks attached to them, were entirely sunk in the ground before these, and were planted in every place at small intervals; these they called spurs'.