It looks to me like a proof with a tarnished obverse, but it's difficult to tell from the photo. You could try taking another photo with the light coming from a different angle. Sadly, I don't think there are any die markings to differentiate proof and currency versions. I have a couple of 1950/1951 brass threepences that are roughly half way between proof and currency, but I put them down as proof because that is the more likely scenario.