Sphinx Benzin Vacuum Oil Company metal/enamel advertising sign

Sphinx Benzin Vacuum Oil Company metal/enamel advertising sign.

This is a single sided convex sign measuring 60 cms wide x 39.5 cms high.

Unknown age. Details of similar signs and Sphinx Benzin Vacuum Oil Company have been fairly hard to come by on the web. I have found a couple of variations of this sign that sold in auctions in the USA during the past few years. Both of those signs were double sided and flat, but otherwise the same wording, colour and graphics.

The condition is fair. There are various areas of missing enamel around the screw holes and in other areas. There is some nibbling around the edges, especially the bottom edge and overall there are many scuff and scratch marks. The rear of the sign has been painted, maybe post production, but does not look recent. There appears to be a carbon coloured under layer between the blue top layer and the base metal.

The sign is made of steel, one of the images shows a magnet holding a piece of paper to the sign.

If anyone is able to add any more information, especially regarding potential age, I would be grateful to hear from you.