Evaluating a Luger finish

Marvin's post below ("S/42 Luger") got me thinking about something that I realize is some 30 years overdue for me! I have until tonight always "eyeballed" a gun's blue percentage in order to judge the % of finish. Tonight I took the time to measure the exposed surface area of a standard military Luger, not counting the strawed parts and came to a calculation of approx 24 square inches of blued metal. I realize or at least believe that on a salt blue luger this would exceed 25 sq inches. I performed these measurements with a flexable (fabric) but accurate tape and tended to fudge a bit to the lesser size as I did not measure grip screws or the small area around them (for example). My revelation is this: a luger could have a completely "white" sideplate and still be 96% blue (97% with a salt blue, all exposed parts counting). If for example, a piece had the sideplate hump worn white and say a 1/4 inch wide strip of holster wear down the entire muzzle ring (.5 inch) and about one half inch of wear on the right frame rail and a half inch missing blue on the grip strap or butt (these are simply offered as typical holster wear examples) this example Luger would come out with a strong 97% blue remaining. I would like to hear comments if this approach seems to better quantify condition. Thanks