It's a Cooke & Lewis Bakau. The axles are made of stainless steel. (As an aside and quality indicator, the first exemplar I bought came with two right-axles and no left-axles [they should be mirror images], so it had to be exchanged.) The Duraplast seat has some (softer?) plastic insert sleeves where the steel axles go in. But there's no material code on those plastic inserts that I can see. I'm wondering if any lubricant is safe on this combination to ease the squeak when I open/close the seat (or the lid; it squeaks just as bad).
The hinges look like this: 
Best Answer
A teflon based lubricant will be inert with respect to plastics and of course, equally inert to steel and iron products. Teflon based lubricants are used in plumbing applications, specifically in faucet and other water valves, as well as on sliding surfaces for some mechanisms such as 3D printers and low-load CNC devices.
Super-lube is one brand name, although it may not be available in your area as such. A quick search for "teflon grease" results in many returns.