This Caltex Motor Oil sign is a bit special. It depicts the earliest variant of their logo - used between 1936-1947. As well as being an early example it features the extra 'Motor Oil' add-on section which I've not seen another example of - if you Google 'Caltex enamel sign', you'll find a number examples of the round section, but I've trawled through Google and reference books and cannot find this variant. 
The sign is double sided featuring a ornately detailed side mounting flange that would have allowed it to come out from the wall of a shop/garage at right angles. 
Condition is excellent for a sign of it's age - the only notable area of corrosion is to the lower left (in the first image) corner. otherwise there is some scratches, ring marks and chipping to the enamel of the surface (pictured) but no other areas of corrosion and only small areas of enamel loss. 
All in all, this sign is a wonderfully rare variant, with good shape, type face and colours. It measures 87.5cm high, 40cm wide and the flange is 6.5cm deep.