Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4070973.
The pin in the cheap "smart" watch I bought for my girlfriend was rusted when we got it, so the buckle didn't last long at all. This is a replacement for that buckle. I'm not sure of the model number of the watch for which this was designed, or if it even had a model number, but in an effort to make this usable by the most people possible, I in including the FreeCAD FCStd file. For the most part, you should only have to modify the original sketch and the rest should follow. I'd double check just to be sure, but still...
This is designed not to use the original or any standard spring-loaded pin, but rather a larger paper clip. Push the paper clip though and snip it off with a small overhang on each side. Using small hammer and an anvil, hammer each end to mushroom the ends, locking the pin in place.
NOTE Due to either a Thingiverse bug or (more likely) shadowbanning, my models no longer show up under the [Newest] listings. If you want to see more of my models, please be sure to 'follow' me. If you print this, it would really help if you'd post a 'make' so that others could find this model.