The compact models with the accessory rail all seem to have reversible mag releases. The SP-01 frame seems to be similar to the P-01, so I'm not surprised that the release is reversible.
The secret, as I noted in another area, is to check the shape of the mag release openings on the grip.
As Angus notes, if the mag release shape is the same on both sides of the grip, you're in business. But, that is not the case with the standard 75B DA/SA, 75B SA, 85B or 85 Combat.