Typically the SM52 does not define its "extended delivery" with an X. If it has a coater is has a longer than standard delivery and it will be a high pile. If it does not have a coater than the 52 can come with 2 different deliverys. Low and high piles. If it has a high pile it will have an H. Your question about the SM52 4P+LX is indeed a 4 color perfector w/ coater and extended high pile delivery. The SM52-4P is a 4 color perfector, no coater and low pile delivery.