Prior to the date code method of dating a knife, one would be able to date a fixed blade knife by the tang stamp, number of spacers in the handle and the material used to make those spacers. Your knife being supposedly from "1973-1986" is a bit incorrect. This doesn't surprise me, because Ebay sellers usually have no idea what they are talking about. So, my point is, if you are buying a knife off of the bay by only the description, you are already in trouble.
1973 began the upright blade stamp. This means you can read the stamp with the blade pointed up. It should read BUCK 118 USA. That particular stamp ran from 1973 through 1885. In 1986 Buck began using the date code system. I prefer to try to keep things simple as far as dating a knife. Things didn't just start and finish in the first and last of the year. If you try to narrow things down to the month something happened you will never date anything, because most of that information isn't out there. Because your knife stamp ran for 12 years, we than go to the handle spacers for more information. From 1973 to 1981 the knife had 4 handle spacers. These spacers were made of Micarta. Earlier spacers used on knifes pre 1969 were made of a material called Bone Hard Fiber, and had a bit different appearance. In 1981 Buck began removing handle spacers. First they removed one in the finger guard area, then in the pommel. This left only 2 spacers, one in the finger guard and one in the pommel. So, from 1973 to 1985 there were 3 different configurations of the knife. Its not just cut and dry 1973-1985. I hope this short lesson helps, I'm not usually this long winded...
The steel could be 440 or 425M depending on when in that 12 year stretch your knife was manufactured...
