Pete,
yes, the two digit serial number for a navy should should be on the bottom of the take-down lever as well as the side plate. People regard this as commercial style marking. But this is true on the military navies as well as on the commercial navies.
The commercial navies will not have any markings on the right side of the receiver. The ONLY marking on the left side of the receiver would be a 'lazy', crown 'N'. By lazy I mean that the crown 'N' will be laying down or parallel to the barrel.
I might add that the commercial 1908 navy (serial number range 51000) may be either a long frame or a short frame.
Big Norm <img border="0" alt="[typing]" title="" src="graemlins/yltype.gif" />