Found out my hand plane was made in 1953 and the frog screw was stripped before I ever touched it
I picked up a Stanley No. 5 at a flea market in Richmond for $18 about 6 months ago and it cut fine at first, so I never took it apart. Last week I finally pulled the frog to clean out like 60 years of sawdust packed behind it and the screw that holds the frog down was already stripped, somebody had cranked it with pliers way before me. I looked up the patent date stamped on the lateral lever and it puts the plane around 1953, which means that stripped screw has probably been hanging on by a thread for decades. The scary part is it still cut decent boards the whole time I owned it, so I had zero clue the whole setup was one hard push away from going out of whack. I got a replacement screw from a guy on a woodworking forum for $6 and now I check the frog screws on every old tool before I use it. If you buy vintage hand tools and never open them up, you're rolling dice on someone else's 40 year old mistake. What's the worst stripped or hidden damage you've found after finally cracking a tool open?