All the Detroit 2-cycles were designated that way, with the cylinder displacement, the block configuration, and the number of cylinders indicated. 4-53 inlines were used for a lot of applications, marine, industrial, and trucks, and the V-types were pretty popular, also. 6V-53's saw a lot of use from the mid-50's to late 60's in medium-duty trucks, air compressors, and some power generators, irrigation pumps, oilfield equipment, etc. Good engines, but NOISY!
Jerry
