<VV> 4 Speed or not???

[rich dixon]

Hi - how do I confirm that I have a 4 speed trans? My car came with a 3 speed and I bought a 4 speed trans from a private party. 

The marking on the case say GM 3; in big large letters and below is the serial # of 3859954.  Is this a 4 speed trans as I was told. Engine and trans out of the car. I am just concerned why is says GM 3? Where can I can a list of serial or case numbers?

Thanks.