Had a similar one last week...splitting the middle of a 24" round and found a huge nail..so glad I didn't find it with a saw. It was in pretty good shape for being in there so long.
Hit an old rust coffee can with the saw yesterday. Trashed the chain, cut can almost in 1/2. Was nailed to a tree I had dropped and I didn't see it.
Yeah on the bottom and the property I'm cutting in has 4ft tall grass/weeds. Dog mushers used to board dogs many years ago there and the cans I think we're for food or water. Have found a ton of rusty cans. I actually stepped IN one and it got stuck in my boot cutting up the back of my ankle. Have found dog chain, moose bones. Couple trash bag of moose guts, a few dead hookers, car parts... You know the usual Alaskan backyard.