The first use of the dog head shield was Union Cut Co in the late teens (circa 1919). There were several different models of knives at that time with the famous dog head shield. These first dog heads will not have KA-BAR on the dog shield. When the KA-BAR brand was adopted in 1923 there were a few models the same as earlier Union Cut models, but now they had KA-BAR on the shield as well as on the tang of the main blade. Several other models were added, but I believe they all were discontinued around 1942 with the onset of WW2. In 1977 the new KA-BAR company (no longer related to the original Union Cut Co.) re-introduced two models of dog head knives in a model that was available pre-WW2. Since then they have made more models with the dog head shields, but they are not models that were the same as the originals. If one studies the shields closely it is easy to tell the difference between the originals and the modern ones. Also the originals were all large knives 4&1/2" closed or larger, whereas there are many newer ones which are smaller knives. There are also known knives stamped Western States and Napanoch which have the dog head shields and these were made on contract for those companies by Union Cut Co.