By the looks of it I'd say it's more likely that the seat tube is 27.2 mm in diameter so you'll need a 27.2 seatpost. You can measure this yourself though, just measure the inside of the seatpost across the middle. I've got a seatpost that would fit that but another forum member (whatamidoing) has it at the moment.
Looking good - any idea who made the frame?
By the looks of it I'd say it's more likely that the seat tube is 27.2 mm in diameter so you'll need a 27.2 seatpost. You can measure this yourself though, just measure the inside of the seatpost across the middle. I've got a seatpost that would fit that but another forum member (whatamidoing) has it at the moment.