The Sedgley 1911 barrel insert was a conversion unit that allowed the M1911 pistol to be converted easily into a single shot 22LR pistol for training purposes.
Once inserted into the M1911 barrel and aligned with the barrel hood. The sleeve would be precisely lined up to allow for the standard M1911 hammer to strike the 22LR rimfire cartridge and the extractor to remove the .22 long rifle casing.
Early units observed with serial numbers less than 1,000 were often inserts, while observed units above 1,000 came inserted already and pressed into a barrel.
Serial number 586 is an earlier insert type. It has the roll mark "R.F. SEDGLEY. INC. PHILA. PA. USA" on the left hand side.