Vega 12b lens versions

I'm looking to purchase a Vega 12b lens. I'm wondering if there is any variation in this lens type, and if there are versions that are better than others. Just so I know what to look out for when purchasing one. It seems like there are at least two versions, one with bronze-colored aperture blades and one with black colored aperture rings. Anyone know which one is better? Are older versions better than newer ones?

Thanks!