This was a rather difficult challenge. Would have been a lot easier if I didn't put silly restrictions on myself.
I started this challenge back in 2008 and was determined to find Soviet coins struck from 1988 to 1991. This must be complete with COA and the boxes. Turns out this was not a good idea. If I decided to go with the coins alone, I would have completed them a long time ago. What makes this remarkable is that there's only 12 coins to this yet it took 6 years to hunt them down; the last coin taking at least three years to find! Please note that I was not actively hunting them down.
Note that starting from this year, there is a huge influx of counterfeit / replica of Soviet silver commemorative coins. These are VERY dangerous counterfeits - you might as well check out
ebay and have a look. Sellers are still honest enough to claim that they are replicas but if you didn't look at them carefully, you can be fooled.
Presenting a couple of the more beautiful Soviet silver commemorative coin (IMHO)


My photography skills aren't the best and as some of these coins were taken a few years back, I wasn't that good in using the older camera (plus inexperience with taking good photos)
So what was the last coin that I was chasing? Turns out it was this coin... I don't know why this was so difficult - I was certain that Captain Cook or the World Children Summit would be a lot harder.

I don't think the box is original however I guess I'll leave it as it is for now.
The rest of the coins can be seen here:
http://gxseries.com/numis/rus_new_t..._ag_comm.htmHope you enjoyed it!
P.S. My recommendation is NOT to start this - unless you want to start chasing them for many years to come. (Or just go for the coins alone)