Well this is supposedly one of the more common hobbies irl but i have literally never seen anyone else online who collects coins. Probably because I'm on the wrong side of the Internet for meeting other coin collectors seeing as it's more of an old people hobby (and I'm not old at all)??? Idk. But even with this hobby I'm an oddball bc I'm not as hardcore about it as seasoned collectors and oldheads are. Grades/conditions of coins don't concern me so much at all- I'm really just after the designs on the coins I like best (I love wheat pennies especially) and their place/time of origin! I also like collecting damaged/corroded coins because those too have truly unique and one-of-a-kind designs (...in the form of damage and corrosion lol). I love me some parking lot patina pennies sometimes. If I encounter coins from other countries I keep those because they interest me (I have a Yemeni coin, a coin from the UAE, a Canadian penny, and several Mexican coins I found) and I also keep otherwise regular coins if the mint year is of some interest to me (I keep 60s coins just because and 40s wartime nickels for their silver content, and I keep coins from my birth year), and often times these criteria for keeps overlap- my friend got me a 1906 silver 10 kopek coin from Imperial Russia as a birthday gift! I'll edit in pictures of some of my coins later if I can find the files in my gallery.
I also am very interested in WWI specifically though it's been some time since I deep-dived on the topic so I'm a little rusty. I do have a desire to collect objects from this period too though, but so far I only have my m1917 British Brodie helmet (again adding pics later) for my "collection". It sits on my shelf and is likely leaking asbestos because the wool in the top interior has long since rotted away 😍 I hope to get more items from the period soon, and one day I hope to have both an original uniform/kit for any country, and a reproduction US kit (I wanna go for an AEF 82nd division impression, because my own grandpa was in the 82nd airborne much later during the Vietnam War) so I can actually wear/use it without potentially damaging historical artifacts. But it can be a very expensive hobby so that's why I haven't added to the collection any further, as well as me having a space issue, I just don't know where I'd keep anything large at the moment. If I add any more pieces to my WWI collection it's probably gonna be smaller items like patches, shrapnel/small trench art pieces, buttons, pins, etc. or things like original period photos and letters.