Mk1 Lotus Cortina Rev Counter Tachometer

Manufacturer: Smiths

Smiths rev counter / tachometer for a Mk1 Lotus Cortina. Noted blemishes are some white dust specs on the inside of the glass which typically means some of the nearly 60 year old screen printing paint is flaking a bit. Also the "earth" or grounding designation has been scrapped off. These cars were usually positive ground so maybe you could conclude this was converted to negative earth? Either way, this should be checked out. Some of the black paint on the ring has rubbed off too. Function of this tach is unknown.