From 04 on they adopted KTMs engine no. system- where the first no. of the engine no. denotes the year:
4 for an 04
7 for an 07
etc
And AFAIK, Husaberg follow the KTM capacity identification by the 2nd, 3rd and 4th digits of the engine no
590= 525
594= 450 (KTM)
etc etc.
Unfortunately I do not have the codes for Husaberg capacities.