Thanks to Noor for the very helpful post on the Russian Forum.
The standard issue of this subject medal was made of silver in various sizes. I have one that is 29.5 mm dia and approx. 19 grams in wt. This one appears to me to be authentic. Can anyone confirm whether this medal was made of other metals? I have one version that is bronze, 28mm dia, approx 15 grams in wt. This is a well struck medal. A third version is made of light weight silver medal but not silver. It is 28mm in dia., approx. 7 grams in wt. I assume this one is a copy although it is possible that it is some sort of war issue. I do have one Russian language reference which comments on "different metals". However, I haven’t managed the translation of the paragraph (a laborious process for a non Russian speaker!) If anyone has any insight on this subject, I would appreciate any comment. Thanks.