Hope i am not bothering you with all this info....
I feel we must try and get the Wenger details going more,
The universal wrench is sad to be from around 1980, atleast this was my information,
Then i found an ad from 1979 with the Windjammer and sailship on the scales, also 1980 did not fit my information, so if this is correct and i hope a new special add arrived in 1977 with the wrench! here they say new tools is made. Also more here i will show link on bottom, so i would say 1976 Universal wrench, also i can say that around 1977 the flatscrewdriver with cap opener changed side.
in the ad they mention two new lines from Wenger: Personalized line and Sportsman Presentation, remember i sad Personalized around 1985 with imprints, Wenger mentioned to me in the 80s they changed or late 80s maybe to another way of printing characters on the scales, again no 100% info.
I have a V.I.P with Rose that should be 1976 knife, so maybe we can say 1976...
Anyway in 1977 they say characters to make it more easy to identify your knife with your interest. All this makes much sence with my late 70s and early 80s knives.
http://books.google.no/books?id=8OMDAAAAMBAJ&pg=PA23&dq=swiss+army+knife&hl=en&ei=qrcxTbnUCsToOceD2bYC&sa=X&oi=book_result&ct=result&resnum=8&ved=0CEQQ6AEwBzgo#v=onepage&q=swiss%20army%20knife&f=false