Piper Cub (J-2) (NC20137)

Thanks for the hint, how can you tell the difference though? Thanks

The J-2 had the Continental A-40, a 40hp engine with the ignition leads coming straight out the heads, as opposed to the J-3's A-65. The cowling is different behind the engine and the vertical fin and rudder are shaped differently than the J-3, all seen here on your photo.