I've been pocketing one of these lately. They were my grandfather's, who passed away just a couple months ago. I was fortunate enough to receive his small collection of pocket knives.
Being a farmer, sheep raiser, and man of the earth, he always had a sharp knife in his pocket. The story was that when he was talking to a farmhand he might hire, he would ask to see the man's pocket knife. If he didn't have one, my grandpa wouldn't hire him. If he had one, my grandpa would try to use the knife to trim a fingernail in one smooth cut. If it wasn't sharp enough to do that, he still wouldn't hire him.
After retiring from farming he was a salesman for MoorMans (livestock feed). I'm guessing these knives were promotional gifts to give to clients.
The Frontier is a model 4131 and has carbon steel blades. I actually have 2 of these. The Buck is a model 303, with stainless steel blades. The box from the Frontier is copyrighted 1975, and he retired from MoorMans in 1981, so obviously they date from between those years. There was no box with the Buck. Any additional information (mfg date on the Buck, steel types) anyone might have on these knives would be greatly appreciated.