I worte this to Mr. Robert Gibson who is an expert on the M1 Carbine. However, the email address I had for him was apprently no good. Not sure if Mr. Gibson reads the Firearms Forum but if you do, here is the message I sent to you. Or, if anyone else can answer my questions, I would appreciate it. Dear Mr. Gibson: I found your article about the M1 Carbine (both in Fulton Armory & Guns World) extremely interesting. I wish now I had read your article before I recently purchased a M1 Carbine from a local Gun Dealer. Although the markings on the barrel do not match up to any of the Contractors listed in your article, I am wondering now if I made the wrong purchase. The barrel markings reflect 'Blue Sky - Arlington, VA.'; the serial number is 4349706. Under the rear sight, just above the serial number, it looks like it stamped "POS-TER". Do you have any information on this M1, when it was made, and who is 'Blue Sky'? Also, I read that you were looking for one from IBM. A friend of mine just lost his dad who had an IBM, Serial Number 3778980, mfg November '42. He will be selling it. Don't know if you are still interested. I have seen it and it looks like it is in very good condition and has been kept in a Temperature Control Gun Safe. How much do you think this M1 is worth? If you are interested, I can give you his contact information, otherwise, I may purchase it and take my loss on 'Blue Sky' version????? Thanks for your assistance and sharing your knowledge.