Mainspring
4.7mm wide, ~~245mm long, with a ‘T’ end. The narrow part of the opening for the mainspring ‘T’ is 2.65mm and the wide part is over 5mm. Perhaps if you can’t find the exact end, I can grind down a spring with no end on it or convert some simple end to work.
![](https://timev3technology.com/wp-content/uploads/2024/01/music-box-mainspring-end-683x1024.jpg)
Mainspring barrel: