HR Mainspring SA743 for Waltham 12s Colonial B No. 2237 / 2269 - Alloy

HR Mainspring SA743 for 12s Waltham Colonial B, Factory No. 2237 / 2269, alloy, new in envelope. See images for precise mainspring specifications. While it's technically NOT a 12s that's the most common designation used, nevertheless this mainspring only fits in the Colonial B model. I likely have several of these so the one you get may differ slightly from the images. I specialize in hard to find watch parts and all watch parts are unconditionally guaranteed. Images do an adequate good job of representing the item.