Good Morning All: I was on gunbroker yesterday and found an odd SBT. The barrel and fore end appear to be S/N 176759 The receiver and trigger guard are S/N 177086 which is strange in and of its self. But what I don't understand is the rib appears to have rectangular posts not round, is this an early style? I did not find any mention of this style in the TPS.
https://www.gunbroker.com/item/854928546