Ok, forced me to look it up. I would go from 1969 to 1972. In 72 the model number was added ( first were early inverted 3 liners) and in 1969 the spacer material was changed from red Bone hard fiber to red micarta. So, it can't be any earlier than 1969,having the micarta spacers we don't know if early, mid or late. Thru setting in on seminars and visiting with many knowledgable collectors who think the stamp changed occured in the last quarter of 71 all the way into the first quarter of 72. This is as close as we can get on either of these dates + or - six months. Much research has been collected on this subject with the 110 and there are 3 versions of this model and this stamp which extend into 1972. So, when dealing with the lack of information one must recognize the 'Buck pattern' among several models inorder to substaintiate a possible date. But I'm confident most collectors more knowledgable than myself would give these dates their approval. DM