Vintage BMC Metal Tin Sign British Motor Corporation Ltd Genuine Auto Car Parts

I'm unsure of the age of this vintage sign, but I have had this for about 22 years, and it was previously owned before I acquired it. It measures 18" x 27". It is made of non-magnetic metal (aluminium?) and has a flat surface, without embossing. There is a screw hole at each corner for mounting to the wall. This has some haziness and spotting that you can see if you tip it to the light. A bit of car wax might fix it. There are a few surface scuffs and scratches in the paint, the most noticeable being through the 'I' in GENUINE (see close-up photo) which shows the white paint beneath. The back side has some glue or varnish on one corner. This sign has no bends or dents. It still looks quite nice and displays well.