I'm not sure it's an SR. Here's a picture of the '81 sr250 I had.
Note that the exhaust header on mine comes out of the front of the engine to the right of the down-tube. Yours comes out to the left of the down-tube and then sweeps across to the right in front of the down-tube.
It looks like the seats could be the same - however, the tanks are definitely different. If yours is an SR, likely at some point a PO fitted a different tank.