How to identify a transmission?

[solocreation]

I own a '02 Spec V and I'm looking to drop an '04 Spec V transmission. From what I've read and been told this is the most favorable transmission for the Sentra especially for autocross. I found a couple of them on Craigslist and I found one with extremely low mileage for $450. I know it's a gamble buying one without having it inspected and word of mouth can turn out to be a $450 pile of elephant dung clinging to my car. For starters, I would like to know if there is a specific serial number or code on the transmission that identifies it? Also is there any access panel for a quick peak? Or do I have to hold it over my head and shake it for rattling parts? All jokes aside any input on this would be much appreciated.

[RED_DET]

02 Spec-V RS6F51H
03 Spec-V RS6F51A
05 Spec-V RS6F51A

Those numbers should be stamped on the transmission. 03-06 should be the same, the only different year was 02.

The H=Helical Limited Slip
The A=Open Differential

[solocreation]

Perfect! Thank you!