Hmmm. Well, these are in the style of mid to late 19th c. belt knives (some call them 'boot knives' as they were often hidden in a boot for quick self defense). These were popular in the U.S. with gamblers and saloon girls (soiled doves), who might wear them in a garder for quick access. The older types were often made in Sheffiled and sold here. Hilt materials for those types were usually ivory. Yours appear a little later (?), perhaps early 20th, but still in the time frame of 'old Western'. Hilt material could be Bakelite, an early plastic from c. 1900. I'm no expert on these, so let's leave room for someone to correct me!
