The Crown Mainspring for South Bend 0s No. 32528 - Steel

The Crown Mainspring for South Bend 0s, Factory No. 32528, steel, new in envelope. I've never heard of the brand before and am a bit suspicious as the keeper for the mainsprings looks remarkably similar to the ones Waltham uses and they were known for making mainsprings for other competing brands under many different names. I check these older mainsprings carefully before I list them all watch parts are unconditionally guaranteed. Images do an adequate job of representing the item.