Swiss SM-67 Gas Mask Review and Test

Review and test of the Swiss SM-67 Gas Mask, used by Switzerland in the cold war, eventually replaced by the SM-74 gas mask, many people confuse the two masks but they are clearly different.
The SM-67 while initially appearing primitive is actually very comfortable and effective. It makes a good facial seal without applying too much pressure to the skull, meaning it can be worn for long periods without discomfort.
In the United States, the SM-74 is often sold for around $20, a very good price, however, in the UK this mask cost £30, the SM-74 doesn't seem to turn up.
The mask came with a very basic carry bag, an anti-dim kit, and a Swiss 40mm filter.