The 1947 - Present Chevrolet & GMC Truck Message Board Network

Not sure where exactly this topic would fit in since it would apply to basically all trucks. I am in a Napco owners group and one member is convinced that the stamping on the frame rails and crossmembers means that the truck was either a state or government purchased vehicle. The circle with an S inside of it- according to him means State owned. However I've seen multiple sources prove this to be the frame supplier/builder AO Smith- its even stated in the GM Chevelle parts book. http://chevellestuff.net/qd/frames.htm
These pictures are of my '56 Chevy 3600 frame, each rail and crossmember has this stamping on it and it was never a state owned or government owned truck. To me this stamping meaning state/government is a far fetched myth. Can someone provide any additional proof that this is indeed the AO Smith stamping to help settle this? Keith?