What do I have?

[imarangemaster]

The serial number is early puts in in the first production serial number block #6 to number #99999, sometime in 1943. Based on barrel date, it sounds like the original barrel and makes it about maybe a month later than the barrel date (just an assumption). It sounds like the typical "mixmaster" carbine that has been upgraded by the military. The flip safety, the adjustable rear sight, and barrel band with bayonet lug would have been added in a later arsenal rebuild and update. Your serial number would have an early flip sight, push button safety, and Type I band with no bayonet lug. 95% or more of the carbines out there now are "mixmasters". That does not make them bad, as they were upgraded for a purpose by the military, and is "as issued" in the later part of its service life. ANY USGI carbine is a GOOD carbine!