Hard to say if the 11-53 LMR barrel is original to the rifle. The majority of the LMR barrels found to be original to late HRA rifles seem to be dated during 1955. Keep in mind that many LMR barrels were used during rebuild programs. Is there a punch mark either within the loop of the P or close to it ?? The P being the one on the barrel. Barrels installed by HRA will have the punch mark in this area. Barrels installed during rebuilds should also have a punch mark in this area but it was often overlooked. What I am trying to say is that the lack of a punch is a good indication the barrel was installed during a rebuild. If it has the punch you will have to look for other indicators of a possible rebuild.