Seatpost clamp size for Brodie Energy 1996?

[LikeClockwork]

As this doesn't look like selling... I am toying with building it up. It's missing the seatpost clamp and it definitely seems to be 30.9 around the outside of top of seat tube..??! Measured with vernier. Is this even a recognised size? As I can't see that it is. Anyone else with a Brodie know the definitive answer? TIA!

 

[joglo]

I had a bit ago a Energry, but rather 98 or 99 year.
This had a 27.2mm seatpost, but needed also a bit unique seat clamp with 30.0mm