Its DT-A - can't tell for sure what capacity bike as they're all the same shape, just different sizes. I'd guess that its a 250/360 one.
The 125 and 175 tanks are the same size, and I think the 100's is also the same.
The 250 and 360 tanks are larger than the 125/175 tanks.
The bolt-on rear mount gives it away as being a DT-A tank, rather than the rubber-band mount on the DT1/RT1 tanks.