series 1 or 2

[burnin240sx]

what series is this ecu?

it comes from a 97 r33

[NISMO_RB25]

I think the 97's were all Series II. I don't know from looking at your pick, but assuming it came with your motor, check to see if you have an ignitor chip mounted to the top of your coil pack cover towards the firewall. If you just have a plug there, Series II

If you have a coil pack, Series I

There are probably a bunch of other ways to tell, but to me that is the quick and easy.