Help who can identify this part

[Jeff Burger]

I have never seen one of these before, I did a search on air tanks but came up empty - It appears to be an air tank to fill up the space saver . Can anyone tell me if this part was delivered by porsche or if not where it belongs? The date code is 1975 and I am pretty sure they were delivering compressors by then.
TIA jeff

[James Brown]

That's a air cylinder to fill the space saver spare. Early one and very rare but don't use it. It needs a hydrostatic test. Best to sell it to someone that needs it for a concourse car.