In 1902, Franz Heger, an Austrian ethnographer, published a study in which he classified the South East Asian bronze drums into four main types known as Heger types I to IV. The Heger classification, which categorized the bronze drums by their shape, dimension, weight, decorative design, chemical composition and casting techniques, has been the key in many past studies. But since 1975, the number of bronze drums discovered in Viet Nam has doubled providing significant new material and theories on the Dong Son culture. Based on these findings, Vietnamese archaeologists have proposed a new classification adapted from Heger's foundation work.

 
 

The Classification of the Dong Son Bronze Drums
Date	Grp	Examples	Size & Shape	Design	Discovery
6BC to 3BC	A	Ngoc Lu Hoang Ha Co Loa Song Da Mieu Mon	Face: 60-70cm dia. Height: 40-50cm; large & proportional; shouder and body of equal dimensions	vivid, rich & composed	mostly in Viet Nam; drums with sloping body were usually found in the highland while those having vertical straight body were mostly found in the plain
5BC to 1BC	B	Duy Tien Yen Tap Phu Duy Dong Son	Face: 56-65cm dia. Height: 47-53cm; slender & tall body	simpler and marked different geometric motifs from Group A	mostly in Viet Nam
4BC to 1AD	C	Hieu Chung Dong Hieu Thanh Van	Face: 34-116cm dia. Height: 24-92cm	sophisticated & stylized as Group A; 4 frog sculptures near the rim of the face	mostly in Viet Nam
4BC to 1AD	D	Dao Xa Tung Lam	Face: 26-52cm dia. Height: 24-38cm heavy body; broad shoulder, steep slope & shorter base	few, simple & crude; Flaws resulted from poor casting techniques	few in Viet Nam & mostly in Southern China
1AD to 4AD	E	Cao Bang	Face: 35-88cm dia. Height: 21-62cm undefined & dispropotional shoulder, body & base	simple & meager; influenced from other cultural forms; some only 1/3 of face	mostly in Southern China

Minh Bui
References:
Lich Su Viet Nam, Phan Huy Le
The Bronze Drums of Dong Son, Nguyen van Huyen et al.., 1989