Developed right after the WW2, KM-16 series of masks was almost, if not excatly, an excat copy of the German Luftwaffe's oxygen mask used during the war. This is easy to see when someone starts comparing early KM-16 versions to the original Luftwaffe design.

At the first glance, KM-16A looks just like the original Luftwaffe mask. Connection to the helmet clearly has German roots - mask has two small elastic straps with metal rounded off hooks located on both sides of the mask. Oxygen hose is made out of rubber and while it looks like the hose on the German mask, Russians started to experiment with similar hoses in mid 1930s so it might be an original design. Oxygen hose connector is a bit different, though looks like it could be interchangable with connectors used on later Soviet masks.

Located on the right side of the mask is a small oval stamp with "KM-16A" written inside. Left side has a similar stamp, but instead of the name of the mask it carries a 3 digit number (unfortunately I do not know what it stands for). On the nose is yet another stamp, this time it's round and filled with circles of smaller diameter.

On the inside, in the nose area, is a stamp with circled number 1 - most likely this refers to the size of mask. Below, where pilot's mouse would be, extends rubber rod with a flattened round head - pilots would bit on it to keep the mask close to the face during hard manuevers. Under it, all the way on the bottom, is a small opening for the oxygen. This opening is covered by an extremely thin rubber cover to to keep dust and other small particles from getting in to the hose.

 

Located on the right side of the mask is a small stamp which tells mask's version.
On the left side is another stamp with 3 numbers.
Front stamp...
KM-16A connects to the helmet via elastic bands located on both sides of the mask. Design of these straps was probably atken from Luftwaffe WW2 oxygen mask.
Inside, in the nose area is a small number 1 inside of the circle. Most likely this number refers to the size of the mask.
View of the bottom inside part of the mask.
Oxygen hose connector to the aircraft's oxygen system.
This style of the connector appears to be interchangable with more modern connectors used on Soviet masks today.
Unlike later versions of KM-16 and other Soviet oxygen masks, KM-16A uses simple rubber hose.
This is how a pilot would have looked like while wearing KM-16A...