the pic i posted is a scan of the stamp and is a normal stamp size. due to it being a scan there will have been some loss of quality. yet it can clearly be seen. 3 to 4 feet distance would not be normal distance viewing for the stamp. stamps, as you said, are usually on an envelope, and the normal viewing distance of an envelope is when its in your hands, which would make it a normal viewing distance of 0.5 to 1 foot. even the scanned reproduction can be comfortably seen at a distance of 1 foot. a real stamp would be even easier to see at a distance of 1 foot.