[Qgis-user] Difference: EPSG 3004 - EPSG 102092

[Paolo]

Hello,
I am a relatively recent QGIS user. I am at the moment using version 2.0 
- Dufour.
I would like to ask a simple question about two different datums I am 
experiencing problems with.
They are: EPSG 102092 and EPSG 3004.
Accordinf to my (short) research, they  are supposed to be exactly the 
same datum, but the definitions in QGIS are different.
If I use 3004, the specific data set I'm using will overlap properly 
with the other datasets, but it will not if I use 102092.
Can anybody help me getting a better understanding of this behaviour?
Thanks
Paolo