Having now measured some dao, here are the stats. 1 is a heavy cleaver, 2-6 are slicers. Measurements of pivot point are very approximate, but all are quite far from the tip, unlike jian. PoB is measured from the guard, pivot point (i.e., centre of percussion) from the tip.
# Length Blade Mass PoB PP
1 88cm/34.5" 71cm/28" 1210g 21cm/8" 34cm/13.5"
2 79cm/31" 66cm/26" 830g 18cm/7" 28cm/11"
3 71cm/28" 58cm/23" 620g 17cm/6.5" 26cm/10"
4 74cm/29" 58cm/23" 520g 14cm/5.5" 20cm/8"
5 74cm/29" 58cm/22.5" 850g 11cm/4.5" 21cm/8"
6 71cm/28" 52cm/20.5" 660g 15cm/6" 20cm/8"
7 46cm/18" 35cm/14" 540g 6cm/2.5" 18cm/7"
8 61cm/24" 49cm/19.5" 690g 12cm/5" 23cm/9"
#1 is military style, probably late 19th century, and indelicate pig of a sword. Similar weight compared to many European cavalry swords of the time.
#2 and #3 are possibly military, but probably not cavalry swords. Probably 19th century.
#4 is a court dao, late 19th century, perhaps for a guard officer.
#5 is a falchion-type dao, with an S-guard. Missing the grip, so the weight should be a little higher and the PoB a little closer in. Could be 18th century.
#6 is a straight dao, also missing the grip. Age unknown, but old.
#7 is a little dao with a knuckle guard (like a butterfly dao, but single). Could be a modern fake.
#8 is a huge knife, no guard. Basically a big Chinese seax. These are often described as "river pirate knives" or similar.