The theory as I understand it is it is relatively easy to draw a wire to a certain diameter and clip pieces of equal length so all will weigh the same. Those, hammered flat provide blanks for coins more exact in size than is easy to obtain by casting such a small denomination. http://www.metaldetectingworld.com/photogalary/wire_ money/index.htm I learn from the above site that I was wrong about the sword and Ivan IV struck both designs with the sword design. All I own are dengas a bit over .3g while kopecks are a bit over .6g. Te site has several pages and many photos for ID help. They are many and mistruck coins make it a lot harder to find a match.
I think this is a pretty good example of why they call it "wire money". Looks like it was hammered out on a wire. Was gifted with this one by a seller. About .5 gram. 15mm at the widest point.
I got this message today from Sergei from the metal detecting site. "Your coin - 1 Kopeck, indeed was struck at the Pskov mint during the reign of Ivan The Terrible (Ivan IV), and before 1547. The lettering says: "Knight and Great Prince of Entire Rus'". On the coin's obverse, there is supposed to be the mint-master's mark - a letter "A", under the horse. "
It's kind of a slog, but I matched up my kopek (an Ivan!) by combing over the forty-some pages on this site: http://www.metaldetectingworld.com/photogalary/wire_ money/pages/01_denga_ivanIII.htm The text on the coin examples isn't always legible, but the legends are typed out below the photos.