The J.C. Harrison book is known for it's incorrect information, not only just the USP relocation.Hi JohnnyP, I relied on J.C. Harrisons Collectors Field Guide, Vol. 4, p.45 for the following: "the United States Property" mark was moved to the right side of the frame above the serial number at about S/N 590,000 or slightly earlier.". After seeing your post I see that Clawsons Third Edition, p. 19 states, "This change was implemented between serial numbers 500000 and 510000.........". Poyer, @ p. 275 says, "At circa serial #510,001....the marking was moved to the right side of the receiver.......". After wishing I hadn't been so quick with the lip, I think that you and Clawson are correct, (What a surprise!). There is a picture on the Clawson page cited above of a right side UPS receiver. SN is 556757, well before "SN 590,000 or slightly earlier". I stand corrected.