What's te difference between a 53 Buick Custom and a 53 Buick Special?

just bought a 4 door 53 buick custom 8 and cant find any info or history on that model. looks exactly like a Special to me ecxept i havent seen a 4 door special anywhere on the net. is that the only diff?|||there were special, super , and roadmaster made in 53,the most popular was the special deluxe four door sedan model 41D, 100,312 built, dont no of any custom model,Then in the super it was the four door riviera sedan model 52, then roadmaster four door sedan model 72R . the word custom i think started approx around 63 64 65 year in the lesabre and skylark and was just a slighty beter interior etc ,but sorry not sure for 1953.