When I lived in California, in the early 80's I met a guy named Sol Geeler who was kind of a sales outlet for Lil David Slingers. He would go around to various golf courses and driving ranges, and ask people to try them out and try to get a response from the on how they liked them. He also carried around some woods that had no insert or sole plates, and asked people to try those too. I asked him why no insert and sole plate, and he told me the wood was harder than the insert or the sole plate. He said those woods were made of Yew Wood (he pronounced it Yaw wood) from south America. He gave me a set of Slingers and told me to play a couple of rounds with them and give him a report. I hit some of those no insert/sole plate woods on the range and they made a very high pitched knock when you hit the ball with them. Sort of like persimmon, but higher pitched!
The Slingers were not too bad as irons go, but if you were in grass deeper than an inch, the club head would go underneath the ball when you swung on it. I also tried a set of Browning 440's, that were a funny looking low profile iron, and they did the same thing! But on close cut grass, those 440's would really knock the ball out there!