Yesterday I added to my collection of Unertl Scopes but have a couple of questions and thought maybe I could get a little help here. I picked up a 1 1/2 target scope, overall condition  I would rate fairly good, it has some surface rust in places and some very hard rust in a couple of spots. The optics on it are fantastic. Now the questions, I was wondering how rare a find is it to get one with very fine wires and a small dot? Second question deals with its age. I have an 1 1/4 target that dates to the mid 50's the sn is 29074, the sn on the new addition is 25131. Would that put the new one in the early 50's or so?  I have no idea how their SN system worked. Any help would be appreciated.
Sam