Good question. Mine are probably the same. They are green, have a "Pt" logo on them and "Made in Austria". No idea what they are. Mine only had leaking seals (white flat ring seals), which I unsuccessfully replaced with an IBC seal (leaked even more) and for now solved by returning the original seals and making a tightener tool to screw them down hard. So far so good, but would love to know where to get spares for the seals and lid if one splits.
Did anyone find the "Pt" company that made the lids, and possibly the tanks?