Congrats to both of you being Newbies or not, you have some interesting finds to make in the coming years. It's not always the big valuable coins or jewelry that you find that makes this hobby enjoyable, it's the small things, like that knife you found. I'll tell you I have found hundreds of coins over the years which is great but some of my best finds were just trinket items. I found a Lone Ranger ring one time, not Worth much, probably it came out of cracker jack box or wherever but to me this was a unique item that I unearth and to me the joy of finding this was worth more than many coins found. So unearthing Jack knives and so on can be a thrill just as much as finding some silver coin which ain't that rare to find, if you hunt in the right areas.
All I can tell you is welcome to the Hobby take it for all it offers the good and the times you don't get much. First off don't get discouraged, the biggest mistake many make is throwing the detector in the closet and forgetting about it. Take it out use it, get to know your detector, wear headphones and listen to the different sounds your detector is telling you what's under the coil. Pretty soon you can tell just by the sound of each item what it is before digging and you don't need any meter to tell you this, you will know this. Next, go slow and overlap your coil swings, every time the people that gets more is not the guy running all over the place it's the guy whom is taking baby steps and overlapping his swings. Remember your coils shape underneath is shaped like a upside down Ice cream cone, wider at the bottom of the coil but once you go down a few inches your coil is like the bottom of that Cone very narrow, see how easy it is to miss targets if you swing your coil without overlapping the coil by at least 50%. Once you have passed over the are you swung over and your satisfied you didn't hear anything, step one shoe in front of the other and overlap your next swing at least 50% over what you just did. Keep doing this and you will be more successful.
I could tell you many more tips but this will start you out ... enjoy and have fun is what's it's all about and please follow the 10 commandments of Metal Detecting and respect pubic and private properties as if they were your own. Always take any garbage you find out after you found it, find the nearest garbage and if you packing bottles and wrappers and other crap into a area make sure you pack it back out with you.
One bad detectorist that don't follow the common sense rules screws future detectors for hunting in those areas. Not saying you are doing these things just use the common sense and respect all properties no matter where you are hunting and for goodness sake cover all holes you made, don't leave any uncovered.
Good luck Hunting and we hope you purse will become overfilled with many goodies.
A1MTD
I hope you enjoy the hobby HH