not sure what this is?

Hi just wondering if anyone can help me, i have a astra van envoy 2000 model, its a 1.6 petrol/lpg. I was looking in the engine bay the other day when i noticed a white bottle behind the engine at the back slightly to the right. When i unscrewed the top of it it had like a little measure stick on it, bit like u have for power steering. Someone told me that mine had machical steering and not power steering due to him not seeing a pump. Also it seems to hidden away for something that needs alot of attention. Any help would be great, thanks