After a year or two absence I am back! I forgot that I was a member of this site. I am well aware of the secret serial numbers but even so cannot view enough of the one on the back of the barrel to positively ID it - I have tried mirrors and plasticine to get an impression and all I positively know is that all three numbers have rounded tops so will be 8 or 9 in all probability. The bottom section of the receiver did have a different serial number so it was apparent that the guns were disassembled and reassembled when the numbers were being obliterated or shortly after. I say this because the old scratch marks on the bottom and top match so that it would be safe to say that the top and bottom sections of the receiver have been together for the duration of the guns existence. I strongly suspect that most if not all of the IRA Thompsons are the same in that the components got mixed at some time early in their history but in most cases this could be neither proven nor disproven.. Mine comes with two original mags, an unmarked one and one with patent dates to Jan 11 1921.