Just got the batteries.
Both show different values:
one says 1241 mAh
the other one 1244 mAh

So i REALY doubt the battery tells the value. If this value is somehow stored in a chip i would expect it to be
1st - exact the same in every battery
2nd - at least somewhat close to the value they say it has.

Anyway - the battery powers the n900 for aprox. 120mins with a radio stream turned on. (screen off!)
I'll try with the original Battery the next days. If i remember right, this is pretty much the same time.

So the battery has probably the same power the original has - and therefore is FAR from the 1930mAh the seller (e_cell) claims it has!

I'll write again in some days when i have some comparison to the original.