Italic and Celtic pounds

Mar 2015
Precisely how big was a pound in 5th century, early 4th century BC Italy?
Precisely how big was a pound in 5th century BC La Tene culture Central Europe?

Since when is the Roman libra, in classical times estimated at 328,9 g, attested in use by weights or artefacts that seem to have round weights?

Roman measures are stated to have been adopted from Hellenic measures. How? From which ones? Euboean measures in use in 5th century BC Athens featured "mina" of 431 g, not 329. What measures did 5th century BC Cumae and Neapolis use? How about Taras and Syracuse?

After the classical period, pound drifted - down. Alleged 328,9 g in "classical" time, 327,6 g for Constantine I, 324 g in 4th to 6th century - and so forth.
The debasement from 328,9 to 327,6 g would, for a sum of £ 1000, make 1,3 kg. About £ 4.
A Celtic gladius could not be absurdly heavy. Brennus had to swing it - nimbly. Plentiful examples of gladii - the heaviest types are 900...1000 g. 3 pounds.
Constantine´s debasement alone would have more than earned Brennus´ Vae Victis sword.

How big was the difference between Italian pound, as used in Rome, and Celtic pound, as used by Senones, as of 387 BC? What was the sum in dispute? Remember that the penalty was just 0,3 % of the principal, as just established.