22786, hope this will help you....
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Dating Buck Fixed Blade 100 Series Knives 1972 to 1986 BY Joe Houser
Group 1 1972- Blade stamped BUCK, XXX, U.S.A. Stamp is upside down or inverted, read with the point down, Guard has two micarta spacers and two aluminum spacers. Pommel has two micarta spacers and one aluminum spacer. A holster style, or Flap over sheath was used and the knife came in a two piece yellow bow.
Group 2 1973-1980 Blade stamped BUCK, XXX, U.S.A. Stamp is right side up, read with the point up, as it is on today's knives. Guard has two micarta and two aluminum spacers. Pommel has two micarta spacers and one aluminum spacer. Holster style, or Flap over sheath still used and the knife originally came in a two piece yellow bow but the switch to a one piece yellow box probably started around 1978.
Group 3 1981 Blade stamped BUCK, XXX, U.S.A. and is oriented the same as the previous group. Guard has one micarta and two aluminum spacers. Pommel has two micarta spacers and one aluminum spacer. I should note that I have only seen the 119, 120, a couple 121s, and one 118 in this configuration and it is likely that the other models skipped this and went straight to the next version. Holster style sheath still possible but also wrap around the handle type is introduced. The belt loop on the 120 swivels. Same one piece yellow box as previous.
Group 4 1981-1986 Blade stamp is still the same as the previous group. Guard has one micarta spacer and two aluminum spacers. Pommel has one micarta and one aluminum spacer. Holster style sheath is still in use on some models. Just about every type of sheath is found in this group. Still the same one piece yellow box as previous.
Group 5 1986- Blades now have a date code following the model number and are stamped BUCK, XXX<, U.S.A. This is the only difference between this group and the one previous. Sheath styles used are probably the same as the group above. Although the logo on the box may have changed slightly, it is still a one piece yellow construction. Over the next many years the boxes used were one piece Black with white letters, then green and tan, category boxes, and now the present orange and black.