It is a legit Russian army surplus gas mask. GP-5 gas mask has been mass produced during the 60s, 70s and 80s in the Soviet Union. The GP5 gas mask on sales has been warehoused for about 40-50 years.
Nowadays old ussr gas mask surplus goes for utilization or recycling. You can look up the production year on the left side of the gas mask. For example, 80… means that your gp5 gas mask has been produced in the year 1980, 3rd quarter.
This russian gp5 gas mask can become a nice addition to your army gas mask military collection. You can wear this soviet gas mask for Halloween or as a post-apocalyptic cosplay costume.