In the past few weeks a vast amount of compressed air bottles for the space saver tire have been sold on this board. These things tend to be expensive and probably of no use that just decoration, since the bottles are to old to refill. (and probably to dangeroud to use anyway)
Strolling through some oldtimer 'parts for sale' sites, I stumbled onto a similar bottle of another german car maker. (Opel Kapitan) I bought it for just 25 euro's and had it powder coated to make it look presentable. It was missing the air tube, but I replaced that with the one that was in the small plastic tyre pump from our baby stroller :)
I think it turned just out fine and good enough for using on a Rgruppe type car or what ever replica car you are building. So it might be something to watch out for if you want a similar item. (Just sharing some info, since I get a lot of info from all you guys, not intending to sell mine)