My latest addition to my collection and my third British mask, CT12. I don't know about the prices of these but I was happy to find one for 13 pounds. It's size
Avon CT12 Gas Mask - YouTube
CT12 Respirator review - YouTube
Avon FM-12 gas mask off scale - DIY Projects & Help - Armed Figures
Vintage U.K. Gas Mask AVON FM12 2004 GB Great Britain 100% original NEW FM-12 S3 | eBay